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.
Black metal
Another major influence on black metal was the Swedish band Bathory. The band, led by Thomas Forsberg (a.k.a. Quorthon), created "the blueprint for Scandinavian black metal". Not only was Bathory's music dark, fast, heavily distorted, lo-fi and with anti-Christian themes, Quorthon was also the first to use the shrieked vocals that came to define black metal. The band played in this style on their first four albums: "Bathory" (1984), "The Return……" (1985), "Under the Sign of the Black Mark" (1987) and "Blood Fire Death" (1988). With "Blood Fire Death" and the two following albums, Bathory pioneered the style that would become known as Viking metal.