Beast Machines: Transformers is a continuation of Beast Wars: Transformers. Fugitives on their own world, the Maximals have to retake Cybertron from Megatron and his army of drones, while adjusting to their new technorganic bodies. The new series opens as Optimus, Cheetor, Black Arachnia and Rattrap discover themselves suddenly back on the Transformer homeworld of Cybertron - with no memory of how they got there. Instead of a hero's welcome for winning the Beast Wars, our heroes are hunted by a mysterious new breed of Transformers - the Vehicons. These vicious machines enforce the will of Megatron, who has returned with a vengeance. Megatron has wrestled possesion of Cybertron, leaving Optimus and his team constantly under fire and on the run.
Set in the future after the events of the original The Transformers and the movie. Beast Wars introduces new classes of Transformers known as the Maximals led by Optimus Primal. And the Predacons led by Megatron. They are descendants of the Autobots and Decepticons. After crashing on a new planet they are forced to take animal form as the planet is largely poisonous to their robot form.