I have no idea why the bands have to be underground. haha Can't they just be really good?
I don't know if it's everywhere, and I'll save myself the rant, but in my area, everyone's obsessed with pretending to be open and "different" by (ironically) closing themselves off from anything that isn't underground/indie. Yet, they buy all their clothes at Hot Topic, which is owned by a corporation. In their attempts to be more individual, they grow together into more of another brand of pop-culture, and, in my eyes, have become nearly indistinguishable from the others who openly follow only what's popular. Only the latter does so without lying to themselves.
I'm not saying you're in that camp - because I don't know you - I was just pointing it out because it's prevalent, at least where I live.
Now that that's out of the way, some bands I think are certainly worth listening to are:
Between the Buried and Me
Cradle of Filth (pre-Nymphetamine)
Ragnarok
Graveworm
Behemoth
Dark Funeral
I've just started listening to Dark Funeral, because up until recently, all I've heard was "Final Ritual" from them, and I thought it was pretty good, so I figured, why not check 'em out. I like what I'm hearing so far, haha.