New York Times film critic Manohla Dargis points out that the good guys in Transformers are mostly fashioned after GM trucks and SUVs. In her review, Dargis calls the film "part car commercial and part military recruitment ad." She also notes that while the Transformers originated as a toy in Japan, curiously none of these robots turns into a Toyota:

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.