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.
Power metal
HammerFall simplified their power metal to bring it closer to traditional heavy metal. This genre spread over Europe, often incorporating further influences from progressive and folk music. Italy's Elvenking, Sweden's Falconer and Denmark's Wuthering Heights are in particular influenced by folk music, while Angra, Kamelot, and especially Symphony X (though none of these 3 are European) are known for combining progressive and power metal. Furthermore, some bands are known for combining power metal with more aggressive musical forms, such as Children of Bodom, who combined elements of power and melodic death metal, or Iced Earth, who combined power and thrash metal. Two Helloween albums, "" (1987) and "" (1988) are usually considered the first proper European power metal albums.