Brats was a Danish (Copenhagen) band formed in 1977 as a punk rock band. Original line-up featured Hank Shermann (real name Rene Krolmark, at that time known as Hank de Wank) on guitar, vocalist Franz De Zaster, drummer Eddie Haircut and bassist Mickey Rat. After recording songs for Danish Pære Punk compilation, the band split up in 1979, not much later reforming as a heavy metal band with new members. Hank Shermann was the only original member left, and he recruited bass guitarist and vocalist Yenz Leonhardt (Jens Arnsted, later of Iron Savior), drummer Lars Monroe and later second guitarist Michael Denner. This line-up signed a contract with CBS.
After one full-length album, 1980 (1980) (re-released on CD by Diamond Records in 1999), Denner left and was replaced by Carsten van Der Volsing. Yenz was replaced with King Diamond on vocals (but remained as bass guitarist). Up to that point, the band was a hybrid of punk and metal, but King didn't want to sing punk rock, so the band started to write heavier songs than before (some of them would later become Mercyful Fate songs, although with different titles and lyrics). It was also at this time, that Krolmark became Shermann. CBS didn't like the new material, so the band quit the contract. Yenz and Monroe left the band, and the rest of the band became Mercyful Fate with new drummer Jan Musen. In 2008, the band released The Lost Tapes: Copenhagen 1979, which was actually their first album, but was never released before.