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.
The History of Heavy Metal
The History of Heavy Metal ("Hårdrockens historia") is a Swedish 2001 documentary movie made for TV spanning through the timeline of heavy metal music. It starts with the roots of heavy metal and ends with the metal of present times. Through interviews and archive material, the movie tries to give answers on many questions, including "which was the first heavy metal band?". It was produced by Malik Bendjelloul and edited by Mikael Björnsson and Johan Larsson for Barracuda Film & TV.