Realistically speaking, Atlanta, GA and a few spots in Florida are the only southern US cities that receive consistent support from metal bands. As has been mentioned, the liberal ideology that is intertwined in most metal music clashes heavily with conservative, southern culture; the result is that most metal bands choose to hold shows in the north-eastern and mid-western parts of the country, where support for such music--and such mindsets--is more widespread.
I currently attend college in a small, north-western Georgian town, and I spend only my summers in Nashville, TN (though I have lived here for almost 20 years now), and sadly, there still is little metal-related interest in the area. There are a few small bars/clubs that book true metal bands (as apposed to the -core crap that's so commonly touted as "metal" and can be seen on-stage at least twice a week at various venues), but for the most part, a tiny downtown site called The Muse is the only place that regularly schedules metal shows (I believe Exodus played there with a bunch of banal -core bands on Tuesday night, and the Suffocation/Cryptopsy/Aborted tour came through that same spot during the week of Thanksgiving).
Looking at future dates, the only concert of note is the Sleep Terror show on Jul 31 at a bar/club called Wallstreet, but that too will probably be crowded with –core bands/fans, as the main member of Sleep Terror wishes to remain removed from the modern death metal crowds.
If you’re looking for music stores that support metal, check out the independently owned/operated store called The Great Escape; its used CD selection is often littered with discarded metal relics.
If you ever want a ride to an out-of-state metal show--and are willing to share gas fees--let me know; I ocassionally take trips down to Atlanta, GA and up to Louisville, KY if a show interests me enough (there are rumors that a reunited Atheist will be playing a warm-up show in Atlanta sometime in July).