Country Metal is something I honestly never expected to hear, but thinking about it now, it makes total sense. With Metal's general feeling of anger, discontent and rebellion, it makes a perfect match for Country's feeling of depression, loss, anger and some angst. Combine the two together, and you get a heavy metal sound with a Southern twang and some Country guitar effects.
Two great bands I've found that play this style are:
Hank Williams III, playing I'm Drunk Again, and a more angsty sounding A Pale Horse Named Death, playing As Black As My Heart.
Both songs are great, generally relaxed, but still have everything that makes them metal. Definitely worth a listen.