@aqua03 no probs. It's one of my favorite subjects. I also forgot to mention that there are even subgenres within subgenres, like Post-Hardcore.
And then there's regional subgenres that influence a certain style of a subgenre, like NYC Hardcore, vs West Coast Hardcore. Or Bay Area Thrash Metal vs Teutonic Thrash Metal. However the regional tags aren't usually applied unless you're explaining the influences of a band, or determining what time period the band came from, and how the region they were from, impacted the scene.
Something that people don't understand is that there's entire sub-cultures attached to the music. It's actually really interesting from an Anthropology standpoint. Unless the listener is an angsty-teen going through a phase, usually a metalhead is very in-tune with the culture involved. It is often a lifestyle moreso than just a taste in music. The culture aspect is just as varied as the music in the subgenre.