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.
Music history of the United States
Heavy metal's early pioneers included the British bands Led Zeppelin and Black Sabbath, though American cult bands Blue Cheer and The Velvet Underground also played a major role. Their music was hard-edged and bluesy, with an often menacing tone that became more pronounced in later subgenres. In the beginning of the 1970s, heavy metal-influenced glam rock arose, and musicians like David Bowie became famous for gender-bending costumes and themes. Glam was followed by mainstream bombastic arena rock and light progressive rock bands becoming mainstream, with bands like Styx and Chicago launching popular careers that lasted most of the decade. Glam metal, a glitzy form of Los Angeles metal, also found a niche audience but limited mainstream success.