As long as they give him some compelling story arc or embrace him from the start as a dyed in the wool heel, he can definitely work.
I once had the idea that Metallo starts out with just some minor but impressive cybernetic prosthetics. Think Metallo on Smallville, minus the kryptonite. Then Lex or Brainiac continues to use him to test Superman's powers, inevitably leaving him defeated and depressed. Then Brainiac or someone gives him the kryptonite and more cybernetics and we get the "I once was a man" pathos as he realizes how much he's lost.
I still see him mainly as hench material though, unless they have him betray his boss, and if so it hopefully wouldn't be Lex. The big bad baldie needs to seem very far ahead of everyone else. I say Metallo works for Brainiac, then Lex betrays them both and steals Corben's heart.