I did dabble in a little metal composition. One thing that gives it a good edge is the much dreaded minor third progression, usually followed by something a little more wholesome, maybe something like i - bIII - bVII - i. Also i - bVII is a pretty standard progression for the verse riff, especially in a lot of old Iron Maiden songs, speaking of which btw, if I had to recommend one song for major inspiration it would be "Phantom of the Opera", try finding a live version with Bruce Dickinson singing.
I don't recommend getting too experimental with drums, except for fills and slow tempo sections (Something I'd definitely recommend), because at high tempo, one very important element is the rythm.
Speaking of which don't be afraid to use a simple straightforward riff for the guitar under the vocals or the solo, because you want to give them center stage. Keep all your creativity for the fills and the sections between the vocals/solo.
Speaking of solos, don't just improvise on the scale, improvise on the chords, you get a much clearer, consistent sound that way.
Also, don't be afraid to use the whole triad for chords, or different kinds of chords for the matter, don't just fall back on powerchords, which are only a good tool if used for high speed verse sections and even then only to accompany the vocals.
Bands I'd recommend:
Iron Maiden (Pretty Catchy and very easy on the ear for non-Metal fans, considering how complex their stuff really is).
Dream Theater (Without the ELP inspired, self indulgent, improv sections, I love ELP... but no)
Old Metallica (Can't get more metal than old metallica)
Tarja Era Nightwish (Two words, effing amazing)
Cryptopsy (Say what you will about Death Metal, but if you REALLY want to be experimental, try listening to a couple of their tunes).
Cynic (Same as above, but a little easier on the ears, a little more melodic and very much more original)
Blind Guardian (Pretty good, and not your typical Power Metal band either)
Cradle of Filth (Not my favorite band, but if you have a keyboardist they are a great source of inspiration)