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. *source : Wikipedia More Details : http://en.wikipedia.org/wiki/Progressive_metal