Not just lyrics, though. Sometimes the negativity extends to cover art too sometimes. I suppose that I am pushing the boundaries of the discussion, though, as my response was at least partly referring to power electronics/noise music as well (stuff like Xenophobic Ejaculation or Zyklon SS).
I think that Drudkh is a highly political band, and their political views seems to come out at least partly through their music itself. However, I never really considered their music to be negative - it seems too romantic and warm for that.
In terms of metal, I was thinking about stuff along the lines of Konflict (whose music videos consisted of clips of various bombings/gunfights from the Sri Lanakan civil war) or Catasexual Urge Motivation (with pictures of gore/corpses as album art). Sometime the negativity seems too strong to just dissolve into the music.