First of all, I dont even know what a preamp does. But whats a good one for HEAVY music (Metallica, Pantera, Slayer), and in the 100-150 price range? Thanks.
Preamp is the part of the amp that does the modification to your sound. Adds distortion, applies EQ, etc. You can purchase them by themselves rather than as part of an amp, which is what I assume you're talking about.

I dont know of anything good in that price range, sorry. Decent preamps tend to be expensive. Mesa makes some REALLY good ones, but they're pretty high up there.
oh my god dude did you just start playing? if so, thats great. but for real; a preamp is the sound mod part of your amp; dist, reverb, delay, etc. most amps now have one built in i highly suggest a Fender G-DEC if you want a decent amp w/ a preamp built in it; but you can buy a Line 6 POD for like 260 USD, which is a preamp that ROCKS!!!
My last.fm
Quote by OMMad
i've always found pop to be harder to play than metal... especially shred metal... it's just really fast tremolo picking and the occasional palm mute... and the only chords you have to worry about are power chords...
Thats good dont know what it is but need to get one. And a good one is going to be hard to find for that money. Maybe a cheaper multi fx pedal for that price.