Initially, when it was a Meltan, Melmetal was prone to fear and it was not used to not following its fellow Meltan friends. However, Melmetal can be a very brave Pokémon whenever its friends were endangered and can be very protective of them as shown when it believed that Ash along with Pikachu were gonna hurt it and Rowlet due to seeing the harm Team Rocket did before they showed up. Melmetal and Rowlet quickly formed a close bond and friendship after meeting one another. Also, much like the relationship with Iris' Axew and Ash's Scraggy in Unova, as well as Ash's Hawlucha and Noivern in Kalos, Melmetal admires Rowlet and views him as a big brother and a role model. As a result, Melmetal instantly trusted and formed a closeness to Ash when Rowlet assured it that he's a very caring trainer towards all Pokémon. In addition, Melmetal was able to become good friends with its other teammates, becoming more outward in general. Also, Melmetal loves to eat metal, especially frying pans, which it can make good use with this ability in many situations. In Ash's battle against Faba in the Manalo Conference, Melmetal is shown to eat Faba's Hypno's metallic pendulum which renders him powerless without it, leading to its defeat. Melmetal has a tendency to act on its own without any input from its trainer. For instance, when Rowlet was in the middle of a battle with Ryuki's Pokémon, Melmetal interrupted the battle by eating the metal decorations on Ryuki's suit. Later, while battling Ryuki's Druddigon, Melmetal tried to use Flash Cannon when it failed to used Headbutt while ignoring Ash's commands in the process. During the search for Ash and Torracat, Melmetal enjoys playing in the snow.
By the time when an official tournament announced, Melmetal became very excited and competitive, especially during its first match by the results of Faba and his Hypnos’ cheating on letting it out to battle them instead of Pikachu, resulting Ash’s mere luck of victory at the 16th-Finals.
After an evolution fusion with the Meltan hordes, Melmetal becomes a bit of muscle brain Pokémon, similar to Buzzwole before it. Also, Melmetal became less of doing things on its own as it became more listening to Ash's commands in battle but does still do it once in awhile.
Meltan was originally sealed alongside its fellow Meltan within the crated located in underwater near Poni Island, until for some reason, the seal was broken and currently only three Meltan who are briefly seen walking underwater.
When Ash and his friends were finished with their studying at Poni Island for their preparation for the upcoming Alolan Pokémon tournament and return to Melemele Island, there were more than three Meltan aside itself who are sneaking on board, hiding in a shadow within the ship's packaging room, eating few metalic substance and making ring sounds.
When they arrived on Melemele Island, Meltan and all of its friends were in a warehouse before they went into the sewer, after they ate the manhole cover. However, They ended up getting separated into two different groups when they were startled by a wild Rattata. Meltan and its group ended up in the Ultra Guardians base where they caused some trouble for Lusamine's Clefable, who was doing some cleaning, until they went upward and into the Pokémon School classroom. Seeing Sophocles toolbox, Meltan with its group ate the metal until they were discovered by Ash and his classmates when Lillie, who accidentally mistaken it for a bolt, picked up one of them. Meltan with its group were observed by Ash and his classmates along with Professor Kukui until they ran away, after they panicked from Kiawe's Marowak flame on his bone when he was doing a greeting dance for them. While its group were wondering around campus, Meltan came back to the classroom and saw Ash's Rowlet sleeping then it decided to take a nap next to him. Meltan woke up from its nap and freaked out by the way Rowlet, who woke up just before it did, was staring at it which caused it's hex nut to fall off. After Rowlet saved its hex nut from a wild Murkrow that was about to grab it, Meltan was very grateful for his help and followed its new friend into Ash's Backpack. Due to being inside Ash's backpack with Rowlet, Meltan was unknowingly brought to Professor Kukui's house by Ash while its friends were at the Ultra Guardians base with Clefable.
Meltan woke up from inside Ash's backpack then saw a frying pan to eat until Rowlet noticed it and grabbed it before Ash or his friends saw it then was put back inside Ash's backpack. While at the Pokémon School, Meltan kept giving Rowlet affection until another wild Murkrow grabbed it. However, Meltan was saved by Rowlet but its hex nut fell off and was found by Team Rocket. Meltan became sad to see its hex gone but Rowlet tried to replace it but saw that the hex nut means a lot to it and decided to help find it. They were able to find the hex nut when they came across Team Rocket, who wanted payback with it due to its other group of friends causing trouble for them when they ate their metal at their base when they became separated from each other. Meltan was almost attack by Meowth's Fury Swipes until Rowlet dove in to protect it and shield it from the Fury Swipes. Seeing Rowlet's determination to keep it safe from harms way and how badly hurt he was getting, Meltan decided to protect its friend and attack Team Rocket with its Flash Cannon attack. After Bewear and Stufful came to take Team Rocket back to their base, Meltan went to make sure Rowlet was alright then saw Ash and Pikachu, who been searching for Rowlet, arrived at their location. At first, Meltan believed that Ash and Pikachu were gonna hurt them until Rowlet assured it that their his friends, Trainer and teammate. Meltan was brought back to the Pokémon School where it reunites with its friends when Clefable brought them to show Ash and his classmates with Professor Kukui the hard work she did to get them to behave.
Although it was happy to see its friends again, Meltan decided that it wanted to be with Rowlet then waved its friends goodbye. When Ash asked it if it wanted to stay with Rowlet, Meltan excitedly told him yes and asked him if it can join his team, which he happily accepted, as it already grew to trust him and knowing that it's gonna be with its friend as teammates. After Ash failed the first try to catch it when he accidentally threw the Poké Ball at its hex nut hole, Meltan was officially caught on the second try and became a new member of Ash's team.
Now an Ultra Guardian member, Meltan visits and greets its old fellow Meltan friends about their new jobs at the Ultra Guardians Base beneath Pokémon School under direction of Clefable, as they reply it to be great. Yesterday before meeting its old fellow Meltan friends again where Pheromosa's invasion started at night, Meltan was sleeping with Rowlet on the top of sofa, before being awakened alongside its fellow Pokémon teammates and Ash by Professor Kukui that Hala was under attack by the said Ultra Beast, but was too late when the Kahuna revealed the said Ultra Beast is after the Z-Crystals from their owners like him and the majorities of Ultra Guardians, and the Ultra Beast's speed is unstoppable for them.
After Kukui's announcement for the first ever Alola Pokémon League, Meltan and the rest of the Pokémon were seen training near the beach.
After arriving with its friends at windy Malie City, Meltan wants to awake Rowlet, but Ash replies that he is always like this and still tired. Upon watching a passing by pack of Eevee, Meltan and Sandy begin to cause trouble, much to Lana's charging. When Shaymin tries to get Mallow's purchased bandanna that got flew away by a powerful wind, Meltan and Sandy follows and helps it. Though Team Rocket ambushes them afterwards, the only thing they forget to remember that Meltan can eat their metal cage trap, but both Meltan, Shaymin and Sandy are being ambushed while escaping, so both Sandy and Meltan fights the Team Rocket off while protecting Shaymin until Ash, Mallow and Lana arrived. While Shaymin heals Sandy who got hit by Sludge Bomb from James' Mareanie, Meltan uses a new move Headbutt, immune to Mareanie's Poison-type attack, with Sandy does the final blow before Stufful and Bewear drags Team Rocket away.
While visiting the Kantonian Gym at Malie City, Meltan got upset when it saw Rowlet losing against Ryuki and his Dragon-type Pokémon, Zwelious, as it went to eat some of the accessories on Ryuki's outfit in retaliation. However, Meltan ended up participating in a double battle with Rowlet where they faced Ryuki's other Dragon-Type Pokémon, Druddigon. During the battle, Meltan learned Harden and defeated Ryuki's Pokémon with a Brave Bird-Flash Cannon combination. After winning the match and went home to Melemele Island, Meltan unknowingly ate Ash's badge from Ryuki, much to Ash and Pikachu's dismay.
Meltan and its friends are summoned by Ash to assist Lana rescuing a Legendary Pokemon Kyogre from an illegal group of hunters. Meltan and Rowlet create a diversion, sending Meltan to eat the illegal hunters' Carvanha-like ship to make its system haywire without the hunters' notices. Once the diversion is complete, but Kyogre went berserk by blind rage, Meltan hop onto Rowlet in time and retreat with their friends to their respective Poke Balls.
Meltan was seen sleeping with with Rowlet in Ash's Backpack, it was later seen with its friends in a fantasy as part Professor Kukui's idea on how to use Z-Moves as a battle strategy. Meltan was seen with it's Trainer, Pikachu and Togedemaru while watching their friends practicing their Z-Moves. Meltan and its friends were then summoned by Ash to assist Sophocles and his Vikavolt training to master their Z-Moves.
Meltan and it friends were training somewhere in the forest, preparing for the Alola League. In the middle of their training, Ash and Torracat were sent in the past, leaving the others to know where they are.  After realizing their friends were missing, Meltan and the others went out and look for them. When they were at Ultra Guardians' Base, Meltan and its hordes had shown its friends how they multiply which impressed them before searching for Ash and Torracat. During their search, they ran into some trouble, such as battling other Pokémon and finding food. Meltan and its friends were tired of their search until Ash and Torracat return from the past. After seeing their return, Meltan and its friends were happy they find them. At Lillie's Mansion, Meltan and its friends were training for Alola League.
Meltan was used in battle against Faba and his Hypno who sent out Meltan on purpose to battle them instead of Pikachu. Meltan was able to defeat Hypno and allow Ash to move on to the quarter-finals by luck, such as eating Hypno's metallic pendulum, rendering the hypnotist Pokémon powerless without it. Meltan was then seen watching Tsareena and Primarina in their battle.
Meltan and its friends were summoned by Ash to cheer him and Rowlet in their battle with Hau and Decidueye. After Ash and Rowlet won the battle, Meltan went out of the Manalo Stadium and called its hordes to come join it at the Alola League.
Before the Finals at the Alola League will begin, Meltan was reunited with its hordes and they soon began a fusion ritual to evolve into one gigantic Melmetal.
After evolving into Melmetal, it shows off its power to its trainer and teammates, especially Rowlet which they were amazed by its evolution and even learns a new move: Double Iron Bash.
When it was time for Ash and Gladion's battle at the finals, Melmetal was used first against Gladion's Silvally. Using the power of its new evolution and new move, Melmetal was initially able to gain the upper hand against Silvally with its raw power and heavy hits compensating for the fact that Silvally was more experienced and graceful. As the battle carried on Gladion instead was forced to change Silvally into a Fighting-type using the RKS System, where after Melmetal was defeated by Sivally after several consecutive super-effective attacks, but not without doing some more damage of its own. It was praised by Ash as he knew it battled hard before he continued his battle with Gladion.
Before Ash's exhibition match with Professor Kukui, Melmetal was training with its trainer as it was trying to mastered its Double Iron Bash move while they are preparing for their battle with Kukui. During the exhibition match, Melmetal was used to battle Professor Kukui's Empoleon and won before losing to his Incineroar.
Following Ash's decision to travel the world, he left Melmetal, along with his other Alolan Pokémon, with Professor Kukui before heading back to Pallet Town.
- Melmetal is the second Pokémon own by Ash that is genderless, the first being Ash's Naganadel.
- Melmetal is both the very first Steel-type Pokémon and Mythical Pokémon owned by Ash and evolved as well. Although the Meltan Evolution Line is not originally from the Alola region on original video game origin lore, anime adaption made this Hex Nut Pokémon Line as an Alolan Pokémon Line.
- Melmetal is one of the two Mythical Pokémon whose with the main characters, the first being a Shaymin and Magearna followed by whom Mallow and Lillie are watching over respectively.
- In its early appearances as a Meltan, Melmetal had the same hex nut color contrast as the other Meltan, but as of the middle of Got Meltan? has its hex nut color contrast being toned down. Its sudden hex nut color change is likely the result of Team Rocket's use on its hex nut for the engine on their donut truck mobile hideout for a short while in the said episode. As of SM138 thanks to an evolution fusion results with other Meltan, Melmetal retains its original hex nut color contrast.
- Melmetal being caught by Ash was likely because it has been predictably foreshadowed by his acquirement of Steelium Z-Crystal from Hapu back in "A Grand Debut!".
- As a Meltan, Melmetal's favorite metallic food appears to be frying pans as seen in the Got Meltan? segment.
- Melmetal is the first Pokémon belonging to Ash to use an Electric-type move after Pikachu followed by Naganadel.
- As a member of Ultra Guardian, despite being genderless, Melmetal wears a sticker that is commonly synchronized to be used by the confirmed male Pokémon members of Ultra Guardians, same goes for Naganadel, while Shaymin is a different case.
- Melmetal is also one of the known expanded Pokémon of Ultra Guardian, who is not one of its original founding Pokémon, the others are Lana's Eevee, Naganadel and Shaymin.
- Melmetal is the heaviest and tallest Pokémon Ash has owned so far.
- Melmetal is the only Pokémon Ash has in his Alola team that has not used a Z-Move.
- ^ SM106: Evolving Research!
- ^ SM109: A Grand Debut!
- ^ SM111: Show Me the Metal!
- ^ SM112: Got Meltan?
- ^ SM114: Beauty is Only Crystal Deep!
- ^ SM115: The Dealer of Destruction!
- ^ SM117: Drawn with the Wind!
- ^ SM118: Aiming for the Top Floor!
- ^ SM120: The One that Didn't Get Away!
- ^ SM122: Spying for the Guy!
- ^ SM123: A Fiery Training Camp Trick!
- ^ SM125: A Timeless Encounter!
- ^ SM126: Pikachu's Exciting Adventure!
- ^ SM127: Chasing Memories, Creating Dreams!
- ^ SM128: League Offenders and Defenders!
- ^ SM130: Battling Besties!
- ^ SM132: Imitation is the Sincerest Form of Strategy!
- ^ SM133: Battling on the Wing!
- ^ SM134: The Road to the Semifinals!
- ^ SM138
- ^ SM141
- ^ SM142
- ^ SM146
At Oak's Lab
At Kukui's house
At Cerise Laboratory