Progressive metal is guitar-driven and often features varying (and sometimes sudden) changes in time signatures. The genre is also known for lending itself to complex and extended guitar solos. Consequently, progressive metal songs can become relatively long. Many Dream Theater songs are more than 10 minutes in length and are broken into subsections.
Progressive rock in general first began in the 1960s. As rock and roll became edgier, bands became more inclined to experiment with their sound. The metal genre went mainstream in the 1970s as Black Sabbath and other metal bands grew in popularity. In the late 1970s and early 1980s Rush incorporated progressive elements into heavier music, and by the mid- to late 1980s bands like Queensryche and Dream Theater began popularizing the progressive metal genre.
Although certainly spawned from progressive rock, progressive metal bands frequently incorporate other musical elements into their sound. Changes in time signature, rhythms and long instrumental solos are characteristic of jazz (more specifically jazz fusion), while other bands have incorporated elements used in classical music, such as the use of strings and woodwind instruments and, especially on concept albums, the use of movements.
Progressive metal, itself a subgenre of rock and metal, has many offshoots. Elements of progressive metal can be found in death metal, black metal, avant-garde metal, industrial metal, metalcore, thrash, mathcore and post-metal, among other genres.
Key progressive metal bands include, among many others, Queensryche, Dream Theater, Fates Warning, Symphony X, Kings X, Atheist, Ayrean, Opeth, Pain of Salvation, and, more recently, Between the Buried and Me, Meshuggah, Protest the Hero, Becoming the Archetype, Extol, Comity and Aletheian.
Important and popular progressive metal albums include "Empire" and "Operation Mindcrime" by Queensryche, "Images and Words" and "Scenes From a Memory" by Dream Theater, "No Exit" by Fates Warning, "Still Life" by Opeth, "Destroy Erase Improve" by Meshuggah and "Alaska" by Between the Buried and Me, among many others.