Metal Sonic (メタルソニック Metaru Sonikku?) is the secondary antagonist in the Sonic the Hedgehog series. He is an evil Badnik[3]version of Sonic the Hedgehog and undoubtedly Dr. Eggman's deadliest creation, built for the sole purpose of destroying Sonic. Deployed during Eggman's operations on Little Planet, Metal Sonic confronted Sonic in battle and lost, though he would repeatedly return to challenge Sonic and his allies. Modeled with extreme accuracy after Sonic, Metal Sonic not only resembles his template but can also imitate his moves and achieve velocities matching and even exceeding that of Sonic.[3]

While mostly serving as Eggman's obedient and silent enforcer, Metal Sonic is an intelligent machine with a very dark side. A cold-hearted, aggressive and ruthless killer, he is obsessed with proving his superiority to Sonic and eliminating him for good to the point where he has rebelled against Eggman more than once to achieve his goal. However, he always fails in the end. To this day, Metal Sonic continues to be one of Sonic's most formidable foes. - Sonic News Network