I've plugged myself into a few online heavy metal communities, and I do fancy myself as an amateur reviewer of metal albums. Here's a few bands that are a little more obscure that I have found that I really, really like:
Sabbat. A British thrash metal band. They were relatively short lived, but their first two albums are really great.
http://www.youtube.com/watch?v=685uHyRbOAE
Sabbat. A Japanese band. Try not to get them confused with the British one. They started around the same time as the British band, have released more albums; but being Japanese, they are a bit more obscure. They play black/thrash metal with large amounts of Venom influence with a nice oriental flair to go with it. They're responsible for my favorite album of all time: The Dwelling, but since that album only has a single hour long song, here's a shorter one.
http://www.youtube.com/watch?v=GB3m-LPts6M
Nokturnal Mortum. A pagan black metal band from Ukraine. I have lots of love for these guys. Their latest two, Weltanshauung and The Voice of Steel, are really epic.
http://www.youtube.com/watch?v=p4ZzqWhvOVA
Just to mix things up, here's something with clean vocals: Wuthering Heights. One of my favorite power metal bands.
http://www.youtube.com/watch?v=uU5n-grrkc8
I think that's enough for now.