Transformers the movie started off with Unicron devouring the planet Lithone. This planet is inhabited by robots and the only survivors were Kranix and his crew. The scene then shifts to the Autobot moonbases where they plan to liberate Cybertron from the clutches of the evil Decepticons. They preparing a supply shuttle for launch to Autobot City on Earth. The communication however, was intercepted by Laserbeak and the Decepticons ended up slaughtering the Autobot crew.
Meanwhile, back on earth, Daniel and Hotrod were fishing and saw the shuttle landing. They raced to meet the shuttle when it lands. Hotrod however discovers that the shuttle is infested with Decepticons and proceeds to blast them The Decepticons then attack and lay siege to the Autobot city.
The Autobots were badly outnumbered with a big chunk of the Decpticon army ramming down their throat. They then sent a signal to Optimus Prime to send reinforcements. Meanwhile, most of the defenses of Autobot city were already breached and there were casualties. To finish off the Autobots the Constructicons merged into Devastator and all seemed lost.
Optimus Prime and the Dinobots arrived just in time and turn the tide of battle. Optimus Prime singlehandedly decimated the Decepticon army and it came down to a one-on-one encounter with Optimus Prime and Megatron. Optimus Prime was set to win and finish off Megatron but Hotrod got in the way and Optimus was fatally wounded. He, however, was able to strike a mortal blow and badly damaged Megatron. Without their leader, the Decepticons hastily retreated.
Optimus would die soon afterward and the Autobot Matrix of Leadership was passed on to Ultra Magnus.
The Decepticons threw the wounded Decepticons including Megatron overboard. The castaway Decepticons were then reformed by Unicron into an elite robot army and Megatron became Galvatron. The Unicrons proceeded to crash in on Starscream’s coronation and obliterate Starscream. Galvatron then became the new Decepticon leader.The Decepticons proceeded to hound Ultra Magnus and the Decepticons and destroy the Matrix. They were able to capture it from Ultra Magnus and badly damage him in the process. After a brief tussle with the Junkions, they are able to make friend with them.The Junkions put Ultra Magnus back together and the Autobots and Junkions proceed to attack Unicron.
Unicron, after an argument with Galvatron, began assaulting Cybertron. The combined forces of the Junkions, Autbots and decepticons assault Unicron with little success. The Autobots go inside Unicron and battle through his internal defenses. Hotrod discovers Galvatron with the Matrix on a chain in his neck. He valiantly battles Galvatron. Throught he battle, he is able to seize the Matrix.Hotrod discovers his destiny to become rodimus Prime and unleashes the power of the Matrix. Unicron is destroyed and Galvatron is hurled into deep space. The Autobots then celebrate under their newfound leader.