From Wikipedia:
The Transformers: The Movie is a 1986 animated feature film based on the animated TV series by the same name. It was released in North America on August 8, 1986 and in the UK on December 5, 1986. The film was directed by Nelson Shin, who produced the original Transformers television series, and features the voices of Eric Idle, Judd Nelson, Leonard Nimoy, Casey Kasem, Robert Stack, Lionel Stander, John Moschitta, Jr., Peter Cullen and Frank Welker. It also marked the final roles for both Orson Welles and Scatman Crothers. The story takes place in 2005, 20 years after the events of the TV series' second season and serves to bridge into the third season. Set to a soundtrack of synth-based incidental music and hard-driving metal music, composed by Vince DiCola, the movie has a decidedly darker tone than the television series, with detailed visuals in Toei Animation's typical anime film styling, and Decepticon villains that are more menacing, killing without hesitation. The film features several grand battles in which a handful of major characters meet their end.
Unicron, a roaming artificial planet, devours robot planet Lithone, and only two inhabitants flee. The evil Decepticons control the Transformers' homeworld, Cybertron. The heroic Autobots are using two of Cybertron's moons as staging areas, preparing to strike against the Decepticons. In need of energon cubes, an Autobot shuttle is readied for launch to Autobot City on Earth. A transmission is intercepted by the Decepticons, who ambush the shuttle and kill its crew, intending to use the ship to infiltrate Autobot City.
On Earth, Daniel Witwicky and Hot Rod fish in a lake near Autobot City, discussing Daniel's loneliness, as his father Spike is on one of the moon bases. They pick up the shuttle's signature, and race up to Lookout Mountain to see it land. They spot the Decepticons and launch a preemptive strike. After a brief battle, the Decepticons attack Autobot City. The Autobots, including Ultra Magnus, Blurr, Springer, Perceptor, and Arcee, transform Autobot City into a fortress. As a siege ensues, Ultra Magnus orders Blaster to radio for assistance from the leader of the Autobots, Optimus Prime. The next morning, Optimus and the Dinobots arrive and successfully repel the Decepticons' attack.
Optimus confronts the Decepticon leader, Megatron. Though Megatron is defeated, Optimus is mortally wounded due to Hot Rod's unintentional interference. Starscream takes command of the Decepticons and retreats with their fallen leader and other wounded aboard Astrotrain.
Perceptor informs the other Autobots that Optimus's wounds are fatal. Before his death, Optimus calls on Ultra Magnus to assume command of the Autobots and tries to give him the Autobot Matrix of Leadership, asserting that the Matrix will one day light the Autobots' darkest hour. The Matrix falls out of Optimus's hand, but is caught by Hot Rod, who passes it to Ultra Magnus. Optimus's monitor then flatlines and he turns grey and dies.
Astrotrain's shortage of fuel prompts the Decepticons to eject several of their injured—including Megatron. The remaining Decepticons argue over who should lead them. The Decepticon castoffs encounter Unicron, who offers to give Megatron and the others new bodies on the condition that they destroy the Autobot Matrix, which Unicron says is the only thing that can defeat him. Megatron reluctantly agrees and Unicron converts him into a new form: the Decepticon warrior "Galvatron". His underlings are reformatted into Cyclonus, Scourge, and the Sweeps. Unicron provides them with a craft in which they travel to Cybertron, where Galvatron obliterates Starscream and re-takes command of the Decepticons.
On Earth, the Autobots are alerted as Unicron consumes Cybertron's moons, along with Autobots Jazz, Bumblebee, Cliffjumper, and Spike. Galvatron leads the Decepticons in another assault on Autobot City. The Autobots board a pair of shuttles and flee toward Cybertron. Hot Rod, Kup and the Dinobots are shot down over the planet Quintessa, while Ultra Magnus and company evade their pursuers and set down on the planet Junk for repairs.
Captured by Quintessa guardsmen, Hot Rod and Kup witness the sentencing and execution of Arbulus, a native of Lithone. While imprisoned they meet Kranix, now Lithone's last survivor, who tells them about Unicron before he is fed to the Sharkticons. Hot Rod and Kup are subjected to a mock trial by Quintesson executioners, who sentence them to execution. Battling the Sharkticons, they are rescued by the arrival of the Dinobots. Grimlock persuades the Sharkticons to rebel against the Quintessons while the Autobots escape. With help from the Dinobots' new ally, Wheelie, the group locates a ship and departs to join the other Autobots.
Galvatron hunts down the Autobots on Junk. Ultra Magnus fails to awaken the Matrix's powers, and is dismembered by the Sweeps. Galvatron, no longer willing to serve Unicron, steals the Matrix, intending to make Unicron his slave. The remaining Autobots are harassed by hostile Junkion natives, led by Wreck-Gar, until Hot Rod's party arrives and befriends them. The Junkions repair Ultra Magnus and provide a vessel to help the Autobots fight against Unicron.
Galvatron attempts to subjugate Unicron using the Matrix but is unable to unleash its power. Unicron transforms into a planet-sized robot and attacks Cybertron. Galvatron opens fire on Unicron, but Unicron swallows him. Decepticons attempt to counter Unicron's attack, to no avail. When the Autobots arrive Hot Rod crashes their ship through one of Unicron's eyes and they find themselves separated within his body. Wreck-Gar and the Junkions fight back against Unicron, but Unicron crushes their ship.
Inside Unicron, Hot Rod confronts Galvatron while Daniel and the other Autobots rescue Spike and the survivors of Unicron's assault on Cybertron's moons. The Autobots and Decepticons work together to fight Unicron. Galvatron tries to assist Hot Rod, knowing that Unicron is a greater threat, only for Unicron to force Galvatron to attack. Hot Rod recovers the Matrix and unleashes its power, transforming him into Rodimus Prime. Rodimus throws Galvatron into space, then unleashes the Matrix's true power, obliterating Unicron. Rodimus leads the Autobots out of Unicron's body before it explodes. The Autobots reclaim Cybertron. Unicron's head orbits Cybertron as a new satellite.
Rated as Universal, suitable for all.