Team Magma was one of the two criminal syndicates active in Hoenn during the storyline of Pokémon Ruby, Sapphire and Emerald, with a goal opposite to Team Aqua's: to expand the land, rather than the sea. In the Pokémon World, Team Magma are a group of thieves/peacemakers in the Hoenn region. They are a team of experts in the fields of geology and plate tectonics. Like Team Rocket, some rebels act as Pokémon thieves. Team Magma specializes in using Fire-type Pokémon. Team Magma's leader is Maxie.
Team Magma often use equipment that is normally used for experiments with high temperatures. They have no vehicles except the Commander's helicopter. Team Magma are bitter rivals of Team Aqua. Though Team Magma does not exist outside the Hoenn region, they do know the work of Team Rocket, who have no Hoenn branch. Team Magma's main purpose is to expand the land mass, believing that by creating more room for life on land that they will be making the world a better place. To that end, they'll awaken Groudon from its slumber.
Team Magma frequently make appearances in Pokémon Advanced, and are seen merely as "big brothers" rather than a proper arch-rival. They eventually disappear after a battle between Groudon and Kyogre. It has been verified that neither Team Aqua nor Team Magma will be appearing in any future Pokémon episodes. Brodie, however, makes one final appearance after the disappearance of Team Magma.
Team Magma grunts often use Zubat, Poochyena, and Numel (In Emerald, they also use Baltoy). Reputed members use Poochyena, Mightyena, Numel, and Camerupt. Maxie uses Golbat, Crobat, Mightyena, and Camerupt. In Pokémon Ultra Sun and Ultra Moon, Maxie also uses Groudon.
Interestingly enough, Team Magma's intentions are similar to the character Faust's in the old German Epic by the same name. At the end of the epic, Faust manages to achieve Maxie's dream of pulling back the oceans to achieve more living land (just how much he pulled back is unknown).