Metal Luigi

Metal Luigi is the metal counterpart to Luigi who currently only made his appearances in Super Smash Bros. Melee and Super Smash Bros. Brawl. He is also the younger twin brother of Metal Mario. He is one of the mid-bosses of the games.

Super Smash Bros. Melee
In Super Smash Bros. Melee, Metal Luigi is one of the game's mid-bosses encountered before the final boss, Bowser. He appears in Adventure Mode, alongside Metal Mario. Once the player has unlocked Luigi, Metal Luigi makes the battle harder, because instead of battling one metal brother, the player has to battle the two metal brothers, who gang up on the player. Like Mario's metal counterpart, Metal Luigi is heavier than the regular Luigi and uses the same moves as his counterpart. Additionally, players can pick up the Metal Box item, turning themseles into metal forms, boasting the same attributes as Metal Luigi and Metal Mario.

KOing both the Metal brothers in Adventure Mode awards the player 8000 points.

Super Smash Bros. Brawl
Metal Luigi has a chance to appear as an opponent on Classic Mode on stages 6, 7, 8, 9, or 10. This will not be guaranteed 100%. Like Metal Mario, Metal Luigi can also be played only on Metal Brawl. His role is very similar to Melee's and he is now able to perform Luigi's Negative Zone.

Trivia

 * In New Super Mario Bros. 2, when Luigi gets a Gold Flower, his body turns to silver, making him look similar to his metal form.