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
The earliest example of folk metal was the English band Golgotha, whose 1984 EP "Dangerous Games" contained a mixture of new wave of British heavy metal and folk styles. The genre was not further developed, however, until the emergence of another English band, Skyclad. Their debut album "The Wayward Sons of Mother Earth" was released in 1990. It was not until 1994 and 1995 that other early contributors in the genre began to emerge from different regions of Europe as well as in Israel. Among these early groups, the Irish band Cruachan and the German band Subway to Sally each spearheaded a different regional variation that over time became known as Celtic metal and medieval metal respectively. Despite their contributions, folk metal remained little known with few representatives during the 1990s. It was not until the early 2000s when the genre exploded into prominence, particularly in Finland with the efforts of such groups as Finntroll, Ensiferum, Korpiklaani, Turisas, and Moonsorrow.