Crystal sent some of her Pokémon, including Metagross, to Emerald who used them in the Battle Dome. Emerald used Metagross in his battle against Dome Ace Tucker and his Charizard. Metagross used Rock Tomb on Charizard, which successfully hit. Charizard then used Overheat and Emerald ordered Metagross to keep using Protect. Metagross wasn't able to endure the Overheat attacks and was knocked out.