Progressive metal is a subgenre of heavy metal and progressive rock, having emerged in the United Kingdom and the United States during the 1970s. Progressive metal mixes elements of heavy metal and progressive rock, taking back its "aggressiveness" and an amplified heavy metal electric guitar sound, accompanied by experimental, complex and "pseudo-classical" compositions. Progressive metal often uses conceptual themes associated with progressive rock. Over the years, progressive metal has been inspired by many other genres, including classical music and jazz fusion.
Although the genre emerged in the late 1980s, it was not until the 1990s that progressive metal became successful. Dream Theater, Queensrÿche, Tool and Fates Warning are just a few examples of progressive metal bands that have achieved commercial success; also, heavy metal bands like Megadeth incorporate elements of progressive music into their songs. The popularity of progressive metal began to decline in the late 1990s, but remains widely popular in the underground scene of the genre.