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.
Rock music in Serbia
The late 1980s also saw the emergence of the first extreme metal acts, which saw little mainstream popularity in Serbia and former Yugoslavia in general during the 1980s. The thrash metal band Heller, formed in 1985, released arguably the first thrash metal album in South-Eastern Europe and was one of the pioneers of Serbian and former Yugoslav extreme metal scene. Another pioneer of the former Yugoslav extreme metal scene, speed/thrash metal band Bombarder, originally based in Sarajevo, moved to Belgrade after the beginning of the Bosnian War, where the band continued to record and perform.