Heavy metal music
Critics disagree over who can be thought of as the first heavy metal band. Most credit either Led Zeppelin or Black Sabbath, with American commentators tending to favour Led Zeppelin and British commentators tending to favour Black Sabbath, though many give equal credit to both. A few commentators—mainly American—argue for other groups including Iron Butterfly, Steppenwolf or Blue Cheer. Deep Purple, the third band in what is sometimes considered the "unholy trinity" of heavy metal (Black Sabbath, Led Zeppelin, and Deep Purple), despite being slightly older than Black Sabbath and Led Zeppelin, fluctuated between many rock styles until late 1969 when they took a heavy metal direction.
Viking metal
Enslaved, formed in Norway in 1991, has also been cited as the first truly Viking metal band, with the 1993 EP by the band, "Hordanes Land", named as the first true Viking metal release. A review of "Eld" (1997) noted that "Among the countless bands who were inspired by Bathory's seminal Viking metal, arguably none were as true to its gospel as Norway's Enslaved, whose utmost commitment even extended to donning vintage Norse armor and outfits on-stage". The band's 1994 debut album "Vikingligr Veldi" had "many melodies being borrowed from ethnic Scandinavian folk music to lend additional authenticity to the vicious, fast-paced black metal". Inspired by Bathory, Enslaved set out to "create Viking metal devoted to retelling Norway's legends and traditions of old – not attacking Christianity by means of its own creation: Satan." Its second album "Frost", also released in 1994, served as "an important release for the extreme music subgenre of Viking metal". Though the previous recordings by Enslaved all featured the same thematic material, "Frost" was the first album that Enslaved described as Viking metal. This album also defined the band's lyrical approach. "Decibel" explains that on "Frost", bassist and vocalist Grutle Kjellson "knew it was time to reclaim the gods and goddesses of his ancestors, especially if it meant his version of things would inevitably clash with the Christianized fairytales so often associated with Nordic myth."