The Autobots, including Optimus Prime, learn of the location of a piece of technology on the moon that could have aided them to victory over the Decepticons in the battle for Cybertron. A select number of humans have known about it, triggering the space race for the first human arrival in the 1960's.
After finding the technology, Optimus Prime revives the inventor and his one-time boss Sentinel Prime in the belief that he will return to rejoin the struggle with the Decepticons but it emerges there is something far more sinister afoot.
Transformers: Dark Of The Moon follows on from a franchise cliché, where the first film is a success and the second film a flop. The cliché means that the director must swap some characters and try to "go back to the beginning" in order to revitalise an otherwise dying franchise (see Star Wars, for example).
Michael Bay does exactly this, removing Megan Fox and replacing her with the completely unknown, but equally good-looking Rosie Huntington-Whiteley. He then uses the most up-to-date technology to create truly dramatic effects as he describes the start of the alien struggles.
On that subject, the effects are truly immense. In a stunning third dimension, Bay's opening sequence is truly outstanding. It is CGI at it's best, perhaps since Avatar. Once this is over though, there are a few shaky moments and one horrific one in the desert that sees Megatron literally sliding in the sand as the animators must have taken a little holiday.
Often in films of high computer graphic content the storyline suffers and Transformers is no different. As the hero from the previous films, Sam Witwicky (Shia LaBeouf), tries to settle down with his new girlfriend (Huntington-Whiteley) he begins to feel inadequate as he struggles to find a new job. Despite this, he still manages to force his way into a top secret Government operation and aid the Autobots in their search despite never really needing to be involved in the story.
The double-cross is far too easily anticipated and the 'shock' element was never there at all. The idea of crashing the plot into real world events (Neil Armstrong on the moon, and the Chernobyl disaster) were interesting, but any half-educated adult may take offence at a cheap cash-in on some of humanity's most important moments.
Worth it for the effects, but a great shame that the storyline and characters are a huge let down.