...Blood to be shed of countless of men,
in the name of revenge and heathenpride...
No more withdraw will be on heathenish ground,
no more mercy will be when Gjallarhorn will sound...
Falkenbach - When Gjallarhorn Will Sound
Metal music is probably the most sub-genred musical genre in the world, with the possible exception of House Music or Techno. I will be the first to admit that some of these sub-sub-genres are plain silly and serve no other purpose than allowing individuals who happen to like some obscure band to bask in their 'uniqueness' describing their favourite band as a Pagan Slavic Politically Incorrect Slightly Thrash Gothic Death Metal with Black Metal Blast Beats.
There is however one sub-genre which I believe warrants a serious mention. That is Viking Metal. As opposed to many of the other sub-genres such as speed metal or thrash metal, Viking Metal unsurprisingly derives its name from the themes and general atmosphere of the music rather than the technical execution or sound.
The 'formal' origins of Viking Metal can be traced more or less to 1988 when the Swedish one man formation Bathory released their/his third album titled Blood, Fire, Death. Bathory i.e. Quorthon has incorporated mythical Norse and Germanic themes in both the artwork as well as the lyrics on the album. The music had a very epic and bombastic sound to it. Bathory has released two more albums which insipered the genre and garnered Quorthon a cult following: Hammerheart and Twilight of the Gods (which happens to be my personal favourite).
The genre can not be pinned down to one specific style of heavy metal. There are bands which have a distinct black metal sound such as for example Enslaved. On the other hand there are some which could easily be classed as death metal, Unleashed with their epic Across The Open Sea is a good example of this. There are more and more bands which distinctly choose to incorporate medieval musical themes in their recordings and choose not to be pinned down in any of the aforementioned genres. A good example of this is Falkenbach and their Magni Blandinn Ok Megintiri record. Not entirely surprisingly a lot of the bands choose to sing in their native tongue and some even write their lyrics in long lost ancient Norwegian, Swedish or Icelandic dialects.
In any case the recurring theme is of course the atmosphere and lore of ancient Norse myth. It has since spawned a number of the aforementioned sub-sub-genres such as: folk metal, celtic metal, pagan metal and probably a lot more....