The climax of the film sees a final showdown between the Autobots, led by Optimus Prime, and the Decepticons, led by Megatron and The Fallen, in Egypt. The Decepticons aim to activate a machine called the Sun Harvester, which will absorb energy from the Earth’s sun to create energon to sustain their war effort.
Sam Witwicky, along with his Autobot allies and a team of military forces, arrive in Egypt to stop the Decepticons from activating the Sun Harvester. Meanwhile, Optimus Prime engages in a fierce battle against Megatron and The Fallen.
During the chaotic battle, Sam and his human allies manage to infiltrate the pyramid where the Sun Harvester is located. With the help of his Autobot friend Bumblebee and the ancient knowledge stored in his mind, Sam is able to activate the Matrix of Leadership, a powerful artifact that can destroy the Sun Harvester.
At the same time, Optimus Prime is gravely wounded in his fight against Megatron and The Fallen. However, he refuses to give up and manages to defeat The Fallen by using the Matrix of Leadership to destroy him.
With The Fallen defeated and the Sun Harvester destroyed, the Decepticons retreat, and the Autobots emerge victorious. Optimus Prime, although severely injured, survives the battle and is hailed as a hero by both the Autobots and the human forces.
In the aftermath of the battle, Sam reunites with his girlfriend Mikaela and his Autobot allies, and they reflect on the sacrifices made to protect Earth from the Decepticons. The film ends with Optimus Prime narrating a message of hope, emphasizing that the battle against evil will continue as long as there are those willing to fight for freedom and justice.