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.
Heavy metal genres
Viking metal is a subgenre of heavy metal music with origins in black metal and Nordic folk music, characterized by a common lyrical and thematic focus on Norse mythology, Norse paganism, and the Viking Age. Its musical style is typically manifested as Nordic folk-influenced black metal. Some common traits include a slow-paced and heavy riffing style, anthemic choruses, use of both clean and harsh vocals, a frequent use of folk instrumentation, and, often, the use of keyboards for atmospheric effect. Viking metal developed in the 1980s through the mid-1990s as a rejection of Satanism and the occult, instead embracing the Vikings and paganism as the leaders of opposition to Christianity. Most Viking metal bands originate from the Nordic countries, and nearly all bands claim that their members descend, directly or indirectly, from Vikings. Bathory, from Sweden, is generally credited with pioneering the genre with its albums "Blood Fire Death" (1988) and "Hammerheart "(1990). Enslaved, Burzum, Emperor, Storm and Falkenbach helped further develop the genre in the early through mid-1990s. The death metal bands Unleashed and Amon Amarth, which emerged during the early 1990s, also adopted Viking themes, broadening the genre from its primarily black metal origin. Other key bands in the genre include Darkwoods My Betrothed, Einherjer, Ensiferum, Moonsorrow, Týr, Thyrfing, and Windir.