Progressive metal (sometimes known as prog metal) is a subgenre of heavy metal, which blends the powerful, guitar-driven sound of metal with the complex compositional structures, odd time signatures, diverse fantasy lyrics and intricate instrumental playing of progressive rock. Many progressive metal bands are also influenced by jazz fusion and classical music. Like progressive rock songs, progressive metal songs are typically much longer than standard metal songs, and are often thematically linked in concept albums.

The mixing of the progressive rock and heavy metal styles can be traced back to the late 1960s and early 1970s. One of England's heaviest progressive rock bands, High Tide, fused the elements of "metal progenitors such as Cream, Blue Cheer, and the Jeff Beck Group" into their sound. Other bands such as King Crimson and Rush were also incorporating metal into their music, as well as Uriah Heep, whose "by-the-books progressive heavy metal made the British band one of the most popular hard rock groups of the early '70s". Rush songs such as "Bastille Day", "Anthem", "By-Tor and Snow Dog", "2112", "The Fountain of Lamneth" and "Something for Nothing" have been cited as some of the earliest examples of progressive metal. Another early practitioner of progressive rock and heavy metal were Lucifer's Friend. However, progressive metal did not develop into a genre of its own until the mid-1980s. Bands such as Crimson Glory, Fates Warning, Queensr?che, and Dream Theater took elements of progressive rock groups (primarily the instrumentation and compositional structure of songs) and merged them with heavy metal styles associated with bands like Judas Priest and Black Sabbath (the former of which had some progressive influences on their early albums). The result could be described as a progressive rock mentality with heavy metal sounds.

Progressive metal can be broken down into countless sub-genres corresponding to certain other styles of music that have influenced progressive metal groups. For example, two bands that are commonly identified as progressive metal, King's X and Opeth, are at opposite ends of the sonic spectrum to one another. King's X are greatly influenced by softer mainstream rock and, in fact, contributed to the growth of grunge, influencing bands like Pearl Jam, whose bassist Jeff Ament once said, "King's X invented grunge.". Opeth's growling vocals and heavy guitars (liberally intermixed with gothic metal-evocative acoustic passages and clean melodic vocals) often see them cited as progressive death metal, yet their vocalist Mikael ?kerfeldt refers to Yes and Camel as major influences in the style of their music.