Celtic Frost's impact on the evolution of European heavy metal cannot be overstated. Along with power metal kings Helloween (and to a lesser degree, Mercyful Fate), Frost's enduring influence on Europe's heavy metal landscape is arguably comparable to Metallica's standing in America. Labelled by critics as "avant-garde" for their radical fusion of violent black metal and elements of classical music, the band represented a distinctly European metal perspective.