Mercyful Fate emerged from Denmark in the early 80's to become one of the most important metal bands of the decade. Characterized by the unique, wailing operatic vocals of one King Diamond (real name Kim Bendix Peterson), openly Satanic lyrics, and crushing riffs by the guitarist duo of Hank Shermann and Michael Denner, the band's first two full-length albums (Melissa and Don't Break The Oath) are essential 80's metal classics, with their lyrical stance causing quite the controversy at the time. But their reign on top was short-lived, as King's Satanic views weren't shared by the rest of the band, and Shermann's desire to play a different form of music forced the breakup of the band around 1985. Diamond took Denner and MF bassist with him and formed his own group, King Diamond, while Shermann formed a hard rock band called Fate. Several years later, Shermann and Denner (long since departed from King's band) hooked up together in a little-known project called Zoser Mez, which may well have precipitated getting Mercyful Fate back together, which they finally did in 1993, featuring all of the original members except drummer Kim Ruzz.

Since the reformation, King Diamond (the band) and Mercyful Fate have co-existed simultaneously, with King singing in both bands and the two bands basically taking turns releasing albums. While the later MF albums are far from bad, they have largely lacked the impact of those first two classics, though the most recent, 9, is probably the best of the new ones.