Metal Mario is a character from the Mario universe, usually being one of the fiercest endgame opponents in Mario sports games or the Super Smash Bros. series.
It is a spin-off of Metal Mario, which is a form of Mario. Metal Mario often plays the role of Mario's rival, suggested by his role in Super Smash Bros.
This is also implied in the Mario Kart games, where he says "Mia mama" as opposed to Mario's "Mama mia" and "Papa" instead of "Mama".
Metal Mario retains many traits of the power-up variant, such as being very slow and not very agile, but being a very powerful character; many games in which he is playable have the stats of larger and more powerful characters such as in Mario Kart and various Mario sports titles.