Danish metal begins with Mercyful Fate in the early 1980s. Copenhagen singer King Diamond (Kim Bendix Petersen, born 1956) combined an abnormally high falsetto (reaching Eb6 in head voice), Satanic lyrical content, and two guitars playing contrapuntally rather than in harmony — an approach that separated Mercyful Fate decisively from the parallel New Wave of British Heavy Metal. Norwegian black metal in the early 1990s (Mayhem, Emperor, Immortal) inherited King Diamond's musical vocabulary and pushed it further, making Denmark the effective parent of that whole scene. D-A-D (formerly Disneyland After Dark, formed 1982) took a straight hard-rock line, and Volbeat (2001) invented an Elvis-Presley-meets-metal formula that reached North American arena scale in the 2010s.

Mercyful Fate formed in Copenhagen in 1981. King Diamond, from a working-class part of the city, is self-taught vocally, and his falsetto redrew the ceiling for 1980s metal singing. The 1983 debut Melissa appears on Kerrang's '50 most important NWOBHM albums,' and Don't Break the Oath (1984) is universally cited as the record the Norwegian black metal bands later worshipped. King Diamond's black-and-white corpse paint face makeup is the direct origin of the same look the Norwegian scene adopted in the early 1990s — the late Euronymous of Mayhem (murdered 1993) said in interviews that 'everything we do started with King Diamond.' In 1985 Diamond launched his solo project; the 1987 record Abigail invented the horror-concept-album template.

King Diamond's falsetto is musical and technical at once — inside a single song he ranges across three or four octaves. Track him reaching Eb6 on the title cut of Melissa and you can hear the vocal line sitting above the guitar's highest register, a placement no other 1980s metal singer would attempt. Then notice Mercyful Fate's two guitars (Hank Shermann and Michael Denner) refuse to harmonise in thirds or fifths — they play independent contrapuntal lines, a completely different architecture from Iron Maiden or Judas Priest twin-lead. Volbeat's 'Still Counting' sells the opposite virtue: Michael Poulsen's deep Elvis-style baritone plus down-tuned riffs delivered a formula perfectly calibrated to North American arena metal.

Start with the title track of Mercyful Fate's Melissa (1983) for the clearest exposure to King Diamond's falsetto and the contrapuntal guitar design. Then King Diamond's solo Abigail (1987) for the horror concept album fully executed. D-A-D's 'Sleeping My Day Away' (1989) is the entry for the hard-rock side, and Volbeat's 'Still Counting' (2007) the entry for contemporary Danish metal. Speakers, loud — the standard directive for metal.

King Diamond's 1980s interviews cited LaVeyan Satanism — the atheistic 1966 Anton LaVey religion — as his philosophical basis, and he has repeatedly explained that this is a rejection of Christianity rather than traditional devil-worship. His bone-cross microphone stand was bought privately from a Copenhagen antique dealer and has toured with him for over forty years. Volbeat's Michael Poulsen was in the death-metal band Corpus Mortem before Volbeat; after his father's sudden death, his deepening love of Elvis Presley — his father's musical passion — shaped what became Volbeat's sound.