Transformers is a franchise by DreamWorks SKG (a company separate from DreamWorks Animation) and the name of the first movie in the series. They are live action movies directed by Michael Bay and produced by Steven Spielberg, incorporating extensive CGI to bring the Autobots and Decepticons to life on screen. The franchise exists in a separate continuity from any of the previous TV series, comic book series, or toy lines.
The first movie reveals that the All Spark, a Cube that has the power to create worlds, was lost in the war between the Autobots and the Decepticons over how to use the it, a war that destroyed their home planet of Cyberton. The Autobots learned that the All Spark may have been found on Earth, and travel there to search for it. Decepticons are also searching Earth for the All Spark and revive Megatron, who had crash landed in the arctic over a century before, and had since been kept in a frozen state since then inside Hoover Dam. During the ensuing battle in a nearby town, involving members of the U.S. military, Autobots and Decepticons, Optimus Prime and Megatron fight it out. Optimus is willing to sacrifice himself to save everyone, but Sam Witwicky pushes the All Spark into Megatron's chest, killing him. The Decepticons that were killed were dropped into the Laurentian Abyss with naval vessels stationed to monitor the area. The Autobots choose to stay on Earth since there is no longer a way to restore their planet.
In the second film, Revenge of the Fallen, shows that other Transformers had visited Earth many millenia before during their search for new Energon sources.
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Teletraan I: the Transformers Wiki
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