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
Traditional heavy metal, also known as classic metal or often simply heavy metal, is the group of bands and artists who play a metal music style similar to the style heard before the genre evolved and splintered into many different styles and subgenres. It is characterized by mid-to-fast-tempo riffs, by thumping basslines, crunchy riffs, extended lead guitar solos, and clean, often high-pitched vocals and anthemic choruses. It is not generally categorized as a subgenre of metal, but the main genre of it. Examples include Black Sabbath, Deep Purple, Led Zeppelin, Judas Priest, Iron Maiden, and Dio.