Quote: "I could join, I don't really do anything "
So, you would join and do nothing?

Hahaha, I'm just kidding!

What musical preferences do you have? Are you into metal too, and if so, what kind of metal?
Quote: "I've been told (by professionals) I'm a pretty good singer"
Aha, that sounds better!

No really, it must be awesome to hear professionals say that about your voice, right?
Did you follow some singing lessons too, or are you plannning on following?
Quote: "at my age I don't exactly have the voice for a metal band"
I don't think age is that important for a metalband. All the great metalbands (like Slayer, Metallica, Megadeth, Iron Maiden, etc...) started out pretty young. You can hear them grow older while listening to the voice of their albums in sequence.
Well, maybe you could do the singing part and Mad Nightmare could do the grunting and/or screaming?
Slayer rules!!! Yeaaah, man!