Metal Sonic is the robotic evil version of Sonic the Hedgehog . He was originally created by Dr. Robotnik to go into the past and later history so that Robotnik becomes ruler in the future, as shown in Sonic CD. His next appearance is in Sonic Heroes in which Sonic, Tails, and Knuckles ("Team Sonic") receive a message from Robotnik declaring that he will take over the world within three days. As they all set out to try and stop him, they find out in the end that it was actually Metal Sonic disguised as Robotnik, who has turned on his creator and has locked him away. In the final battle, Sonic and his friends defeat both forms of Metal Sonic and shut him down, presumably for good. His current whereabouts are unknown.
- He is a playable character in the racing game, Sonic R.
- Metal Sonic makes a brief appearance in Sonic Adventure, contained inside a tube in Dr Robotnik's base, near the Mystic Ruins. He also features in the DX version of the game as an unlockable character for acquiring all 130 emblems.
- Although not in the story, he can be chosen in the 2-Player Battle mode of Sonic Adventure 2: Battle.
- He appears as one of the new additions to Mario & Sonic at the Olympic Winter Games.
- As DLC, he is playable racer in Sonic & Sega All-Stars Racing, complete with his own unique vehicle, the Metal Booster, as well as the Maximum Overdrive All-Star Move, a unique racing track, and additional background music.
- Metal Sonic appeared at the end of Sonic The Hedgehog 4: Episode 1 after beating the game with all seven Chaos Emeralds collected, foreshadowing his appearance in Sonic The Hedgehog 4: Episode 2.
- He features in Sonic Free Riders as a playable character, and he is also included in the story mode.
- Metal Sonic appears as a rival boss battle for Classic Sonic in Sonic Generations, recreating the race against him from Sonic CD's Stardust Speedway.