A Metal Mushroom (in some games replaced by either a Metal Cap or Metal Box) is one of Mario's Power-Ups that appears in a few newer games in the Mario series. If Mario eats one, he will transform into Metal Mario and will be invincible for a short period of time. He can also dash into enemies without taking any damage and walk on lava. Mario is also so heavy that he'll sink down in the water, and can't go up by it's stream.