[Muad'Dib]

Could classify Tool as lots, maybe metal isnt term for all their music, but IMO they are progressive. Prog-rock?? Dont know for sure, below is interesting part from wikipedia.

Whether you read it or not I found it interesting.


Arguments About Genre & Categorization
Although Tool's music does not vary greatly in style and technique from album to album (excepting the changes that occur foremost in mood), it is difficult to define their place in reference to traditional musical genres because of their experimental approach to music. Tool are inarguably a part of the rock genre, but just where they fall in that genre and how much influence past groups have exerted on Tool is the subject of intense debate among both fans and casual listeners.

In many cases, Tool are categorized as alternative metal, a broad label used to loosely categorize bands (such as Jane's Addiction, Rage Against the Machine, and Faith No More, among others) that straddle the line between the aesthetics and fanbases of metal and alternative rock. But because the term is used more often as an umbrella for bands that blur categories rather than share particular stylistic traits, it is difficult to analyze Tool in conjunction with other alternative metal bands in genre terms.

Some consider Tool to be, above all else, a progressive rock (or "prog") band. Those who feel that Tool are progressive rock artists frequently cite the popular (and admittedly broad) definition of prog. It is a style of rock music that seeks to move away from the mainstream by "pushing the envelope" of the rock genre, creating new sounds and styles that often possess a characteristically high level of layering and complexity. Tool certainly possess these things, often making use of polyrhythms, dissonance, and highly technical, unusual, and specialized musical techniques, such as Justin Chancellor's bass performance in the song "Disposition". In addition, many of their songs feature complex time signatures: "The Grudge" is written in 10/8, "Schism" in or 5/8 to 7/8 (or in 6.5/8 according Justin Chancellor), and "Lateralus" moves from 9/8 to 8/8 to 7/8.

Beyond the broad definition of prog as an experimental art form, however, lies much debate about what really makes a band part of the prog scene. Even the most commonly cited prog bands, such as Rush, Pink Floyd and Emerson Lake and Palmer, challenge the entire notion of the genre by pointing out either implicitly or in their own words the vast differences in sound and style between each of the so-called "prog bands".

Perhaps the band most cited as a Tool influence is King Crimson, admittedly a favorite group of Tool themselves. King Crimson are listed at the forefront of progressive rock and frequently mentioned as a way to establish Tool's place in prog using the transitive property. Longtime King Crimson member Robert Fripp has expressed disdain for the term as an oversimplification, and in an interview with Tool, touched briefly on how the two bands relate to each other:

Robert Fripp: I was very impressed that the visuals and the band were all part of the same performance. It was... seamless. It was something like, "These guys are playing to the same track." But without being external to the film... There was an integrity to it all.
Danny Carey: Thanks... We all kind of grew up listening to you.
...
Maynard James Keenan (referring to an upcoming concert tour): First of all we're terrified to go on after you, and second of all we're gonna have all these kids in the audience going, "Hey, TOOL ripped these guys off blind!"
Danny Carey: It feels like that sometimes, for sure!
Robert Fripp: Do you hear the influence? There's just one figure where I hear an influence, just one. It was a piece we were developing that we dropped. And it's almost exactly the same figure: three note arpeggio with a particular accent from the guitar. So I don't think you could have heard it. That's the only thing.
Tool Army exclusive interview
So even among the band and their peers there still remains a debate, not only about their place in progressive rock but also about just how closely they resemble their progenitors who are themselves are only debatably established in the genre.

When Tool are not called prog, they are typically referred to as some sub-category of metal. Many have argued that Tool belongs in the nu-metal genre, due to their great influence within the genre. Maynard James Keenan's unique style of singing has been repeatedly seen influencing new artists, such as Pete Loeffler (of Chevelle), Aaron Lewis (of Staind), David Draiman (of Disturbed) and Steve Richards (of Taproot). Others would include Fred Durst (of Limp Bizkit), who calls Tool one of his "most favorite bands in the world" [6], although this association is especially prone to debate, due to the noticeable difference between Durst's (usually) rapped vocals, and Keenan's style, which does not include rapping.

This conclusion is thought of by many to be incorrect, citing the backwardness of this logic. If such were applied in other cases, the blues artists who influenced Led Zeppelin could be argued as belonging to hard rock, or the salsa artists who influenced The Mars Volta could be thought of as aggro in some sense.

Tool are sometimes given an extended genre that would appear to be specific to the band, such as "psychedelic math metal" (see MTV News: The Pain of Perfection) - as other bands that have defied a common classification have. They have also been listed under many genres that people do not normally consider them to be a part of, such as jazz rock (a slight reinforcer to progressive rock assertions), and sometimes even trip-hop, although this occurs mostly as an allusion to a unique live set that featured Tricky.

How well one accepts any of the applied classifications is often a matter of taste. Many people are displeased that "genre theory" is being applied to Tool at all, arguing that far too often genre classification is useless or even limiting.