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
Another British band, Iron Maiden, brought epic and melodic sensibility to metal, creating anthemic, singalong music, an approach widely embraced by modern power metal musicians. The emergence of the early German power metal scene in particular was made possible by Scorpions and Accept. Swedish guitarist Yngwie Malmsteen made a significant impact on many future power metal guitarists, with his accurate and fast neo-classical style. His bandmate Jens Johansson modernized the keyboard sound of Deep Purple's Jon Lord, which was further incorporated into the genre. Manowar's mythological sword and sorcery lyrics influenced a number of power metal bands. In 1987 Helloween released their second album, "", cited by Allmusic as "a landmark recording that remains arguably the single most influential power metal album to date. Its volatile combination of power and melody would inspire an entire generation of metal bands".