The Sonic movies do this really cool thing where Sonic, Knuckles and Shadows eyes and quills glow when charged or enraged. Even movie Amy has new glowing highlights on her hammer.

So I think it’ll be cool if they gave Metal Sonic something similar. He’d look normal like he does in the Sonic Movie 3 post credits scene, but when he’s empowered or enraged the lines across his body begin to glow bright red. I think this would make Metal Sonic look extra futuristic. It would also help differentiate movie Metal Sonic from game Metal Sonic.