Warning! Spoilers ahead!
The movie was quite lengthy, around 2 1/2 hours long. It starting to reveal more history of Transformers in this movie.
The movie started in 15,000 BC when the first Transformer landed on Earth.
Then, it moved to Shanghai China where a Decepticons were detected. Demolisher and Sideways. Both are crushed by the Autobots and human alliance. Demolisher warned ahead "Fallen is coming for revenge".
Sam enrolled to college and President aides wanted Autobots to leave the planet. Soundwave then initiated to revive Megatron by stealing the last fragment of All Spark while Sam accidentally touched the other fragment of All Spark gave him the information of a secret location in his mind. While the Autobots were busy keep the Decepticons at bay, Ravage managed to steal the All Spark and revived Megatron.
Sam then, bumped to a pretender Decepticon female who wanted to kill him. Megatron revived, took back his role as the leader of the Decepticon under a new master, the Fallen. Decepticons then caught Sam and they ambushed Optimus Prime. Optimus Prime was killed by Decepticons.
Desperate to look Sam, the Decepticons then went for manhunt through the mass media, urging to give up Sam or they will destroy Earth.
Sam then with helps with the fallen agent and a robot called Wheelie with "Megan" found an old Decepticon named Jetfire. Jetfire then now defected as Autobot helped Sam and the rest and revealed the history of Fallen and the Primes.
Sam then found out that Matrix could save Optimus Prime and also can activate the "Harvester" that will drain the sun's energy for form Energons.
Decepticons then launched a mass attack on the Autobots and the humans, particulary Sam. Sam managed to revive Optimus Prime but he's too weak to go against Fallen. The old dying Jetfire then took his life to spare his parts for OP. OP crushed Fallen and almost killed Megatron. Ending....
I liked the movie but its a bit draggy towards the end. Many non-Transformers fans would wonder what is Matrix. Many would not understand either on the history of Transformers. This movie is equally as the first one. Michael Bay did it again! Kudos! I can't wait now for Part 3!!