Transformers One is an animated prequel that explores the origins of the Transformers, an alien race of metallic humanoids that can transform into vehicles. It delves into the roots of the conflict between the franchise's rival groups: the Autobots and the Decepticons.

Cybertron is now being led by Optimus Prime, which upsets Megatron. Optimus Prime orders Megatron to leave and never return, exiling him. Megatron promises that it is not over as he and his Decepticons leave the planet.