Tool has forced its American fans to become a patient bunch.

First, devotees had to wait years between albums. Then fans gradually learned to dismiss most information about the reigning kings of melodic metal as the band continually thumbed its nose at the media, offering up false rumors. Last, the Tool army watched the band tour Europe and even more far-flung venues this year, teasing its U.S. audience with a handful of shows that sold out in less than minutes.

They don’t have to be patient anymore.

Creators of the recently platinum “Lateralus” will shower their starving Maine listeners with some musical love at a Sept. 20 show at the Cumberland County Civic Center in Portland, in a show also featuring Faith No More frontman Mike Patton’s newest project, Fantomas.

And what a sweaty, screaming, seductive shower it will be.

For many metal fans, Tool is the ultimate marriage of meaning and might. Insightful lyrics, such as those from the band’s last single, “Schism,” dig comfortable holes in the listener’s soul. Complex layering of instrumental sounds and vocalist Maynard James Keenan’s emotional delivery produce a frenzied yet coherent energy. As “Schism” explains: “I know the pieces fit/’cuz I watched them fall away.”

Though Tool has been heralded by DJs, music critics and most importantly, metal fans, since 1992’s breakthrough (and gold) album “Opiate,” the group has not let that praise hold them back. Tool’s sound has evolved from a stripped-down cacophony to something akin to a symphonic sonic boom. Through this growth, however, the structural integrity of the band’s sound has remained.

Tool won attention with “Opiate’s” no-nonsense lyrics and hard-core sound. In songs such as “Hush,” the band laid the groundwork for its anti-establishment image. The lyrics: “I can say what I want to/Even if I’m not serious/I can say what I want to/Even if I’m just kidding” are followed by a potentially offensive suggestion for those who disagree with that sentiment.

“Lateralus,” the latest in Tool’s musical evolution, is worlds away from the band’s not-so-humble beginnings. Sounds created by drummer Danny Carey, bassist Justin Chancellor, guitarist Adam Jones and Keenan have become blended enough to produce a wave of music in which vocals and instruments seem to weave in and out of a whole, in a manner strangely akin to orchestral music. The term “orchestral” might be the best way to describe some pieces, which stretch way beyond the four-minute margin, and include interestingly reflective pieces “Parabol” and “Parabola.” These vivid extrapolations on a theme, coupled with unconventional time measures, make an album that may not be easy to understand the first time through, but, like the band, evolves into a strange wholeness after several listenings.

Although the show will be Tool’s first in several years in Maine, and the first in which they will exhibit the brave new sounds of “Lateralus,” for some local fans, the sound of Keenan’s voice is not such a distant memory. Keenan’s side project, A Perfect Circle, visited Lewiston in March to perform music from their debut release “Mer de Noms.”

Though Keenan also contributes lead vocals for A Perfect Circle, the group is not another Tool. APC features Keenan’s lyrics in a much more traditional manner than Tool, with the overall sound being more like basic guitar-driven rock – every strum by bassist Paz Lenchantin quivered the bleachers of the Central Maine Civic Center – with the bare rock-band sound upgraded by some technologically advanced musicianship.

Composer and guitarist Billy Howerdel, along with Keenan, do explore some of the same themes as Tool has used in its music, including some potentially controversial references to God and sometimes more specifically Christianity. “Judith” expresses, in Keenan’s words, “blind faith” through references to Christ and those who “never thought to question why,” echoing “Opiate’s” “Jesus Christ why don’t you come save my life.” In interviews featured on the bands’ Web sites, members often deny any direct slam on religion, preferring to refer to the lyrics as artistic metaphor.

APC has created its own solid fan base with hits such as “Judith” and “Three Libras,” and dabbles a bit in the alternative. The group uses its own unique runes-type alphabet, which invites fans to “crack the code” with clues from the lyrics, an artistic puzzle also reminiscent of Tool.

Tool’s bizarre music videos, such as that for the popular “Sober” (off 1993’s multiplatinum “Undertow”), leave some viewers groping for a larger meaning and others simply enjoying the strange visions. Revealing the band’s appreciation for weird art and semi-animation – Jones worked on special effects for films such as “Terminator 2,” and Keenan will play Satan in the film “Bikini Bandits Go to Hell” – the videos feature humanistic creatures pulling themselves apart and stumbling blindly through bleak landscapes. Tool also has taken cover art to a higher form with its layered, medical-textbooklike insert in “Lateralus,” a kind of follow-up to the 3-D pictures and similar work on “Undertow” and 1996’s “Aenima.”

With these kinds of wild artistic ventures laid out in the band’s studio work, one can only imagine what a live Tool show will be like.