Metal Sonic (or Metallix in the Sonic the Comic continuity) is, as his name implies, a robot doppelganger of Sonic the Hedgehog, created by Dr. Eggman. While he is by no means the first, that honour going to Silver Sonic, he is the most recurring, and arguably the most lethal.
With his jet turbine, Metal is capable of matching Sonic for speed, and is somewhat vicious in battle, never tiring and able to attack repeatedly without showing any signs of fatigue. He is also capable of generating a black shield, has a laser housed in his chest and once held the ability to shapeshift. Unusually for a robot, Metal Sonic can be considered certifiably insane, as he has been shown to believe that he is, in fact, the real Sonic.
In his first appearance, Metal Sonic was working alongside his master in seizing control of the Little Planet through altering history. In order to keep Sonic busy and eventually kill him, he captured Amy Rose, and later engaged Sonic in a race in Stardust Speedway, a conflict which Sonic won. In his next major role, Metal Sonic had been upgraded by Dr. Eggman with shapeshifting and DNA absorbing abilities. He quickly went rogue, imprisoning Eggman within his own flying fortress, captured Big the Cat's pet, Froggy and Chocola the Chao to gain the power of Chaos, God of destruction, and set about gathering DNA data on Sonic, Shadow and their respective allies and rivals. He also kept the twelve heroes busy by imitating Dr. Eggman and causing havoc with the villain's air fleet and army of robots. The conflict came to a head when Metal Sonic blew up a good chunk of the fortress and heavily upgraded himself into an enormous dragon-like form. After battling Teams Rose, Chaotix and Dark, he grew a set of wings and tried to flee, but was brought down by Team Sonic, Super Sonic leading the charge. Back on the fortress, as the storm clouds cleared, he resumed his usual form and collapsed, later ending up in the arms of E-123 Omega, with Shadow looking on.
For a time, Metal Sonic managed to maintain a degree of autonomy and worked outside Dr. Eggman's control, seeking his own means of destroying Sonic. However, the robot would ally himself with Eggman Nega, helping the madman accomplish his goal of destroying the entire world. Yet again, Metal would be defeated by Sonic and his allies and later fall back into Dr. Eggman's service, this time reduced to a mindless automaton to ensure that he would not go rogue again.
- Super Speed - Like the real Sonic, Metal Sonic is capable of achieving Mach speeds and can run at speeds that rival Sonic.
- Flight - The turbine engine housed in Metal's torso is his main method of locomotion. He rarely uses his legs to run and instead hovers just above the ground, but is also capable of flying, something that the real Sonic cannot do.
- Black Shield - An energy field that protects Metal Sonic from all attacks.
- Laser - This weapon is fired from the cavity in Metal Sonic's torso. Given the location of the weapon, its targetting range is limited.
- Maximum Overdrive - Metal Sonic's most powerful attack. He generates a destructive energy field as he accelerates to top speed, scorching a long path ahead of him.