Optimus Prime is the leader of the autobots and the cybertronian protagonist of the film series.
Optimus Prime arrives on Earth at the same time as Ironhide, Jazz and Ratchet, landing in a field. He scans the new alternate mode of a semi-truck and quickly joins up with Bumblebee and his human companions. The Autobots then go with Sam Witwicky to retrieve his ancestor's glasses, on which a map to the All Spark is engraved. While waiting for Sam and Mikaela to find the glasses, Optimus and his comrades inadvertently destroy the backyard of Sam's parents. They recover the glasses, but a secret government organization, Sector 7, arrests Sam and Mikaela, and capture Bumblebee. Before it is discovered, Sector 7 also has a frozen Megatron hidden under Hoover Dam, Ironhide questions Prime on why they should protect the humans, seeing them as primitive and violent. Prime replies that the Autobots themselves were not so different from them once, quoting "Freedom is the right of all sentient beings." Before the final battle with Megatron, he says, "By the end of this day, one shall stand, one shall fall." This is a tribute to the 1986 animated film, in which Optimus Prime delivers the line, "One shall stand, one shall fall." before his final battle with Megatron.
While evacuating the All Spark from Hoover Dam, Optimus Prime attempts to thwart the Decepticon Bonecrusher's pursuit. After a short battle, Prime beheads Bonecrusher with his retractable blade. Although Prime fights Megatron in a final battle, Sam kills Megatron ramming the All Spark into his chest. Prime, who had planned to destroy the All Spark by placing it into his own chest, is immensely grateful to Sam for saving him. Afterwards, Optimus then takes the remaining fragment of the All Spark. Despite all that has happened, Prime deeply regrets Megatron's death, evidenced by his parting words: "You left me no choice, brother." In the comic adaptation of the film Optimus and Megatron refer to each as "brother" several times, but in the film, only once. What "brother" means to a Cybertronian is never explained in the film.
Like the other Autobots featured in the film, he chooses to remain on Earth after the battle with the Decepticons. The film ends with Optimus sending out a deep-space signal, inviting other Autobots to join them on Earth.
Optimus Prime returns in Transformers: Revenge of the Fallen, taking down in Shanghai, China, the massive Decepticon Demolishor. Before his death, Demolishor warns Optimus that "The Fallen shall rise again". Later, U.S. defense advisor Galloway chastises Optimus for the damages done during the fight and deems that the Decepticons only remain on Earth to hunt down the Autobots. Though Optimus warns him that there's a chance he might be wrong while telling him the Autobots would leave if requested, he attempts to ask Sam for help. He later fights (and overpowers) Megatron, Starscream and Grindor on his own to protect Sam from the three Decepticons. Though he manages to kill Grindor, and rip Starscream's arm off, Optimus is destroyed by Megatron, who stabs him in the chest from behind, killing him as he searches for Sam. However, learning that the Matrix could revive Optimus (who is the only one capable of defeating the Fallen, since being the last Prime), Sam has his body transported to Egypt for the final battle. He is revived once Sam puts the Matrix of leadership into his circuits. However, the Fallen steals the Matrix soon afterward and uses it to power the Sun Harvester. Jetfire sacrifices his life to give his parts to Optimus. With the help of Ratchet and Jolt, Optimus uses parts from Jetfire as a flying armor and successfully kills the Fallen, forcing Megatron and the Decepticons to retreat. At the end of the film, he again transmits a message to space in hopes to find more Autobots.
==Transfprmers Dark of the Moon
He is seen in the Transformers: Dark of the Moon Super Bowl TV spot combined with his trailer and flying over Bumblebee and Ratchet as they shoot at Brawll, Starscream, and some other Decepticons in Chicago. He then lands, tackling Brawl to the ground, then he shoots at Long Haul, and impales Sideways on his sword. He is then seen slicing an unknown Decepticon in half. He is seen again in the second TV spot, standing behind behind Sam and Sergant Epps, loading his brand new machine gun.