Metal vocalist?
hmm..

M. Shadows (A7X)
Corey Taylor (Slipknot/Stone Sour)
Wednesday 13 (Murderdolls/Wednesday 13)
James Hetfield (Metallica)
Marilyn Manson

Really? I saw A7X live (Festival) and he sucked big time.
James Hetfield is alright, although he did make better music when he couldn't sing.
Marilyn Manson scares the **** out of me, his voice is nothing special though.

Corey Taylor is an excellent choice though, I don't like Slipknot but I saw Stone Sour an they were great.

That would be Matt Barlow.

I really dig Opeth's singer, actually

^Definitely versatile. The best monster vox in the biz, coupled with one of the sweetest voices.

Mikael Akerfeldt(Opeth), Roy Kahn(Kamelot), and Christian Alvestam(former Scar Symmetry) really stand out in the metal scene in terms of vocals. Spencer Chamberlain(Underoath) and Eric Kalsbeek(Textures) are also very talented vocalists as well.

I always find that with metal, good vocals are not really a necessity but if a band has it, they gain an extra edge and add the icing to a cake of riffs, bass lines, and drum fills.