I almost brought up Corey, but I think Slipknot might be too polarizing so I decided not to. He for sure can sing, which most of these metal guys can't.
I would guess that a lot more of them can sing than you think. Also, while not traditional singing, it take a lot of practice/technique/skill to be able to do vocals like all the crazy scream stuff and not blow out your vocal chords. Any vocals/singing will mess you up if you're out touring and not taking care of yourself.
Not the same type of screams, but some of my favorites that do both well