an blue robot, not a real mobian, copy of sonic, Eggman is Metal Sonic's creator. His facial expression is always frowning and angry because it's designed that way, he can't change his facial expression. Earlier he could not speak due to lack of built-in speaker, but now he is able to speak

Metal Sonic was created by Dr. Eggman years ago as a means of countering Sonic the Hedgehog. After his first couple of defeats at the hedgehog's hands, Eggman began studying Sonic's abilities in-depth, using all the data he had accumulated from previous battles to program Metal.

He can't feel emotions. His eyes are completely black, and his cornea is bright red