Despite being built to match Sonic the Hedgehog in all aspects, Metal is vastly different from his organic counterpart in terms of personality. Rather than fun-loving, cool, and carefree, Metal Sonic is a violent, aggressive, cold-hearted, and intelligent killing machine with a large superiority complex. Early on though, he had a habit of mimicking Sonic's gestures, perhaps in a mocking manner.
While he is usually another of Robotnik's mindless robot slaves, Metal Sonic possesses an AI that grants him sentience (though he is still restricted by his programming). This trait, however, has only been used by Metal Sonic to fuel his dark goals of destruction and domination and allowed his programming to evolve beyond what had been intended more than once. At most times, Metal Sonic is emotionless and completely obedient to Dr. Robotnik. Beneath this facade, however, he carries a deep desire for vengeance. When facing a foe, Metal Sonic usually remains quiet and coldly serious, making him a silent killer in a literal sense.