The surprising transformation here is not from machines into enormous robots but from a modest Saturday morning cartoon based on a line of toys into 2007’s most exhilarating summer movie, able to transform audiences of all ages into 12-year-old fanboys.

The robots are just so cool.

The humans are cool, too. This summer’s Most Valuable Player, Shia LeBeouf (already in the season’s best thriller, Disturbia and the adorable animated Surf’s Up) plays Sam, grandson of an arctic explorer who may have uncovered a cube of great power. His new car seems to have a Herbie-esque mind of its own, expressing itself through the songs on its radio.

A race of giant robots who can transform into ordinary-looking machinery like boom boxes and cars has come to earth in search of the cube. The good guy robots are led by Optiumus Prime and like humans. The bad guy robots are led by Megatron and would be fine with the result of their capture of the cube being the destruction of all human life as well. Most of the movie consists of their fights with the humans on and in their way and with each other and the adventures of the humans who try to stop or help them.

Director Michael Bay ably manages the pacing of the action, comedy, and romance, never letting us get tired despite an almost 2 1/2 hour running time. He knows how to hit the sweet spot between the nostalgic affection felt by kids who grew up back when we still called the shows “cartoons,” not “animation” and winning over those who have no previous connection and just want to see some slam-bang robot-on-robot action. He knows the movie is about the robots and gives us robots to swoon over, brilliantly constructed, every rivet filled with both personality and possibilities. The special effects wizardry is seamless, every movement logical and believable, every interaction with the surrounding environs magestic and weighty. And each of them has his own utterly engaging personality. One can only speak through clips recorded from songs and movies. Another has feet with wheels and races along like a speed skater. Another talks like he’s been listening to hip-hop. And the good guy robots have such friendly and expressive eyes. I admit it, I got a little misty when it looked like one of them might not make it.

And Bay gives us humans who are every bit as engaging as well. LeBoeuf is superb as Sam, struggling with parents who want him to improve his grades and do his chores, trying to figure out how to talk to a pretty girl (Megan Fox), figuring out why his new car seems to have a mind of its own, oh, and being entrusted with the future of the planet. Josh Duhamel and Tyrese Gibson as survivors of a robot attack on a US military outpost in Qatar strike just the right note of conviction and all-American heroism. John Turturro as a bully from a secret federal agency and John Voight as the Secretary of Defense provide additional depth and interest.

The Transformers, like other kid favorites Power Rangers, Pokemon, and Teenage Mutant Ninja Turtles as well as comic book superheroes from Captain America to the Fantastic Four, tap into the fascination and the fantasy of being able to tap into a hidden source of transformational power (“more than meets the eye”). This idea has special appeal to kids, who are very aware of their vulnerability and curious about the power the adults around them exercise, the power they may have as they get older, and to young teens, on the brink of their own transformations. When a young human character inspires the devotion and loyalty of the powerful creatures (think of Aladdin, or even Elliot and E.T.), that adds to the story’s attraction, another way to tap into the dream of hidden strength.

And then there is the idea of The Ghost in the Machine, the personality that we project on to the gadgets and equipment that make modern life possible, it is we who find ourselves transformed, into fans — who will never look at our cars, boom-boxes, and cell phones the same way again and who, for 2 1/2 happy hours, will believe in enormous, friendly robots.

Parents should know that this film has non-stop “action” violence, which means a lot of peril, robot-on-robot action, and property destruction but no blood, serious onscreen injuries, or deaths. There is some potty humor, there are some crude double-entrendres that middle-schoolers will find edgy (and funny), and there are some vulgar sexual references and brief drug and alcohol references. A mother asks her son if he has been masturbating. A character gives the finger and characters use some mild language (“bitch,” “ho”). Parents should also be aware that while the movie is PG-13, it is being heavily marketed to younger children through the sale of toys and other tie-ins. The Campaign for a Commercial-Free Childhood has filed a complaint with the Federal Trade Commission, asking them to work with the media and toy industries to establish a consistent set of ratings for toys and the media they are based on and to establish clear, enforceable guidelines for the marketing of PG-13 movies.

Families who see this movie should talk about what Optiumus Prime thinks makes the human race worth saving and what has made the Transformers popular over the years. What things will you look back on in 50 years and be glad that you did?

Families who enjoy this film will also enjoy some of the earlier versions of the Transformers and movies like The Iron Giant, Men in Black and the animated The Transformers movie.