Whom
Yeah, I second "Ombra Mai Fu" and anything from "Messiah," those are very popular contralto pieces. I'd suggest going on YouTube and looking for anything by Marian Anderson, Kathleen Ferrier, and Ewa Podles and see if you find something you would want to sing, they're great contraltos.
Also, if you're female, keep in mind that a tenor singing a metal song is probably singing in the highest part of his voice, and if you sang it in the same key you would be singing in a lower part of your voice. That means that you'll be missing some of the "oomph" that a tenor would get.
My mother actually got me a Ferrier CD for Xmas because she really wants me to sing Mahler's Kindertotenlieder. (I have yet to listen to it.)
I am female, but my comfortable range runs from low C to high A, with higher notes easily attained with head voice. Two years ago I wanted to sing "Every valley shall be exalted" from Messiah, but my choir director (playing as audition coach) pretty much said, "It sounds great, but that's a *really* popular piece and other tenors auditioning might sing it as well."
As for metal singers, I dunno, Heri Joensen (Týr) and Russell Allen (Symphony X) have phenomenal ranges/voices. ^_^ Till Lindemann (Rammstein) however, is definitely a bass.