Boys and their toys are in full formation in “Transformers,” a movie of epically assaultive noise and nonsense. Originating with the shape-shifting toys — created in Japan, rebranded in America — that transform from robots into stuff like cars and planes, then back again, the movie has been designed as the ultimate in shock-and-awe entertainment. The result is part car commercial, part military recruitment ad, a bumper-to-bumper pileup of big cars, big guns and, as befits its recently weaned target demographic, big breasts.

First introduced in 1984, just in time for the rise of geek culture, the Transformer toys have spawned comic books, television shows, video games, an animated feature and a fan base that has grown beyond children to include collectors like Steven Spielberg, an executive producer for the new movie. Not surprisingly, there’s a touch of mawkish Spielbergian sentiment in the movie’s empathetic hook, a riff on the boy and his alien friendship from “E.T. the Extra-Terrestrial.” This time the boy is Sam Witwicky (Shia LaBeouf, talking fast, running hard), a high schooler who discovers that his dingy 1970s Camaro is actually a gentle giant of a robot, Bumblebee.

There’s more — a few goofy caricatures, some throwaway laughs, a lot of technological gobbledygook, the usual filler. Written by Alex Kurtzman and Roberto Orci, who cobbled the story together with John Rogers, the movie takes flight with a raucous, confusing attack on an American military base in Qatar. There, under the desert sun, muscly, sweaty military types (Josh Duhamel, Tyrese Gibson) clash with an ominous helicopter that converts into a mysteriously angry critter with an articulated tail like that of a scorpion. Back in the United States the secretary of defense (Jon Voight) barks orders at other military types while Sam juggles his weird ride, his mounting fear and his agitated hormones.

The guy charged with keeping the movie in gear is the director Michael Bay, the hard-core action savant whose other big-screen eruptions include “The Rock,” “Armageddon,” “Pearl Harbor” and “Bad Boys II.” Like his last effort, “The Island,” this new flick isn’t as propulsive and casually sadistic as the movies that he made with the producer Jerry Bruckheimer (this carries a reasonable PG-13); it feels slower, more tamped down than the usual Bruckheimer assaults. The camera, or rather multiple cameras, are still shooting every which way, and the cutting sometimes registers as eye-blink fast, but not compulsively so. Mr. Bay allows himself to linger here and there, which explains the bloated, almost two-and-a-half-hour running time.

On the face of it “Transformers” is a story as old as the Greeks versus the Trojans, the difference being that these warriors are visitors from another planet, the 1980s-sounding Cybertron, and there isn’t a jot of poetry, tragedy, beauty, meaning or interest in this fight. The Autobots are trying to locate some all-important cube that looks like a Borg starship from “Star Trek: The Next Generation” before it’s found by the Autobots’ villainous alien brethren, the Decepticons. During their mission the Autobots blend into the earthly backdrop by turning into zippy cars and mondo trucks, a strategy that works particularly well in Southern California. Curiously, though the toys originated in Japan, no robot changes into a Toyota.

It’s kind of nifty when the robots transform the first time; they furiously shake back and forth like wet dogs desperately to dry off. But by the 99th time there’s no fun left at all, even during the rock-’em, sock-’em knockdown that delivers the movie, in Spielbergesque pastiche, first to a violent and then to a warm-and-fuzzy close. The actors tend to be more engaging, notably Mr. LaBeouf, who brings energy and a semi-straight face to the dumbest setup. Just as easy on the eyes, though for other reasons, are the two female leads, the genius hacker in throw-her-down heels (Rachael Taylor) and the grease-monkey bombshell (Megan Fox) who helps Sam rise to the manly occasion. These walking, talking dolls register as less human and believable than the Transformers, which may be why they were even allowed inside this boy’s club.

The movie waves the flag equally for Detroit and the military, if to no coherent end. Last year the director of General Motors brand-marketing and advertising clarified how the company’s cars were integral to the movie: “It’s a story of good versus evil. Our cars are the good guys.” And sure enough, most of the Autobots take the shape of GM vehicles, including Ratchet (a Hummer H2) and Ironhide (a TopKick pickup truck). The only Autobot that doesn’t wear that troubled automaker’s logo is the leader, Optimus Prime (a generic 18-wheeler tractor). Maybe that’s because the company didn’t want to be represented by a character that promises to blow itself up for the greater good, as Optimus does, especially one based on a child’s toy.

Shape-shifters of another kind, Hollywood action movies bend this way and that politically in a bid to please as many viewers as possible, but they almost always play out exactly the same, as entertaining violence leads to heroic individualism leads to the restoration of order. “Transformers” is no different, even if it does offer chewy distraction for the bored viewer: the would-be suicide bomber, American soldiers tearing it up in the Middle East while American cars keep up the fight at home, along with plugs for Burger King, Lockheed Martin, Mountain Dew and the Department of Defense. Why there’s even a president who asks for a Ding Dong. He’s wearing red socks like a big old clown, but no one really laughs.

“Transformers” is rated PG-13 (Parents strongly cautioned.) Lots of bang and boom; little to no blood.

TRANSFORMERS

Opens today nationwide.

Directed by Michael Bay; written by Roberto Orci and Alex Kurtzman, based on a story by John Rogers, Mr. Orci and Mr. Kurtzman and Hasbro’s Transformers action figures; director of photography, Mitchell Amundsen; edited by Paul Rubell, Glen Scantlebury and Thomas A. Muldoon; music by Steve Jablonsky; production designer, Jeff Mann; special visual effects by Industrial Light & Magic; produced by Don Murphy, Tom DeSanto, Lorenzo di Bonaventura and Ian Bryce; released by DreamWorks Pictures and Paramount Pictures. Running time: 144 minutes.

WITH: Shia LaBeouf (Sam Witwicky), Tyrese Gibson (Technical Sergeant Epps), Josh Duhamel (Captain Lennox), Anthony Anderson (Glen Whitmann), Megan Fox (Mikaela Banes), Rachael Taylor (Maggie Madsen), John Turturro (Agent Simmons) and Jon Voight (Defense Secretary John Keller).

WITH THE VOICES OF: Peter Cullen (Optimus Prime), Hugo Weaving (Megatron), Mark Ryan (Bumblebee), Jess Harnell (Ironhide/Barricade), Robert Foxworth (Ratchet), Jimmie Wood (Bonecrusher), Darius McCrary (Autobot Jazz), Charlie Adler (Starscream) and Reno Wilson (Decepticon Frenzy).