Metal Sonic in Heroes was voiced by Ryan Drummond, who basically just used his Sonic voice with heavy robotic filters to make it sound more sinister. Sometimes it's tough to tell, but other times you can totally hear it.

Even if I'm not personally a fan of Metal speaking, if he was to talk, this is definitely how you'd want to do it.

It makes me wonder though, has anyone tried to replicate that filter with Sonic's other actors like Roger Craig Smith or Jason Griffith? Or in general, perhaps perfecting the whole execution of the idea so that you do hear more "Sonic" in Metal's voice? Just to see what result that could give?

I haven't found anything when looking for examples, but it could be cool to see brought to life no matter the outcome.