Metal Mario is the sub-boss of All-Star Battlemania 2. Like Onslaught, he is unplayable. He is a re-textured version of Mario, making his body completely metal grey. You will always fight Metal Mario on the Warzone stage.
Metal Mario possesses the same moves as Mario. However, he is technically a clone character as he has a slower movement speed and will never jump. Several of his moves seem to do a bit more damage than Mario's. At long range Metal Mario tends to throw fireballs. His main way of attacking is usually a down-special into his normals.
Upon beating Metal Mario, you are taken to fight the final boss, Onslaught.