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 music
Thrash soon began to evolve and split into more extreme metal genres. "Slayer's music was directly responsible for the rise of death metal," according to MTV News. The NWOBHM band Venom was also an important progenitor. The death metal movement in both North America and Europe adopted and emphasized the elements of blasphemy and diabolism employed by such acts. Florida's Death, San Francisco Bay Area's Possessed, and Ohio's Necrophagia are recognized as seminal bands in the style. Both groups have been credited with inspiring the subgenre's name, the latter via its 1984 demo "Death Metal" and the song "Death Metal", from its 1985 debut album "Seven Churches" (1985). In the late 1980s and early 1990s, Swedish death metal became notable and melodic forms of death metal were created.