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.
Extreme metal
When extreme metal band Hellhammer first began making music, it was generally panned by critics, leading to the members forming Celtic Frost in its place, which proved very influential on the progression of the genre. During this period, the line between extreme metal genres were blurred, as thrash metal bands such Slayer, Sepultura, Sodom, Destruction and Kreator were integral to the first wave black metal scene. The front cover of the Sarcófago's 1987 debut album, "I.N.R.I.", is regarded as a great influence on black metal's corpse paint style make-up. That record is also considered one of the first wave black metal albums that helped shape the genre. Their second album, "The Laws of Scourge", was one of the first technical death metal records to be released.
Genres influenced by extreme metal but usually not considered extreme themselves: