http://en.wikipedia.org/wiki/Progressive_metal
Progressive metal (sometimes shortened to prog metal) is a fusion genre; a mixture of progressive rock and heavy metal. Progressive metal blends the powerful, guitar-driven sound of metal with the complex compositional structures, odd time signatures, and intricate instrumental playing of progressive rock. Some progressive metal bands are also influenced by jazz fusion and classical music. Like progressive rock songs, progressive metal songs are usually much longer than standard metal songs, and they are often thematically linked in concept albums. As a result, progressive metal is rarely heard on mainstream radio and video programs.
The origins of progressive metal can be traced back to progressive rock bands from the late 1960s and early to mid-1970s such as Yes, Pink Floyd, Emerson, Lake and Palmer, Jethro Tull, King Crimson, Genesis, Gentle Giant, Focus, Renaissance, The Alan Parsons Project, early Queen, Kansas, Atomic Rooster, Uriah Heep and Rush. The latter five also often blended metal elements into their music. However, progressive metal did not develop into a genre of its own until the mid-1980s. Bands such as Fates Warning, Queensrÿche and Dream Theater took elements of these progressive rock groups – primarily the instrumentation and compositional structure of songs – and merged them with heavy metal styles associated with early Metallica, Megadeth and Iron Maiden. The result could be described as a progressive rock mentality with heavy metal sounds.
The three flagship bands for prog metal of the time each had somewhat different sounds. Queensryche had by far the most melodic sound of the three and was ultimately the most commercially successful. Dream Theater drew most from traditional prog rock and also built much of their earlier career on the band members' instrumental skills, though later in their career they would abandon much of their more obvious prog rock influences (while retaining their prog complexity, however) in favor of a more edgy, modern prog metal sound. Fates Warning were the most aggressive and heavy and arguably had the most in common with the thrash and extreme metal scenes of the time, which led them to be the least accessible of the three bands, though they also had their own brief taste of commercial success with their Parallels album.
Progressive metal received mainstream exposure in the early 1990s when Queensrÿche's "Silent Lucidity" (from 1990's Empire) became a radio and MTV hit. It was not a typical progressive metal song, but its popularity increased the profile of other progressive metal bands. In 1993, Dream Theater's "Pull Me Under" (from 1992's Images and Words) became popular on radio and MTV. In the 1990s, bands such as Pain of Salvation, Tool, Opeth, Threshold, Symphony X and the project Ayreon developed their own signature sounds.
Pain of Salvation drew heavily on more obscure 1970s prog acts. Ayreon stayed with the traditional Prog Metal themes, but mixed them with many other influences, rock opera and ambient among more prominent ones. Symphony X married progressive elements to power metal and classical music. Steve Vai's former singer and heavy metal band Strapping Young Lad's singer and guitarist Devin Townsend combined elements of post metal and ambient with traditional progressive metal on his first two solo albums Ocean Machine: Biomech and Infinity. Opeth and Between the Buried and Me combined their prog influence with death metal. Another influence on prog metal were "technical metal" bands, such as Watchtower, Atheist, and Cynic, who utilized complex song structures and technical instrumental playing.
