In this chapter, Megatron will attempt to retrieve the Omega key from Zeta Prime. He is supported by Soundwave and Breakdown.
Enter the Stellar Galleries
At the start, enemy autobots will attack from a long range from across the river. These enemies will take cover behind a shield, and should be attacked between rounds. When they are defeated, you can head through the door behind the autobots.
The first room has an ambush, with autobots attacking from the sides. Again, defeating them will allow progress outside, where you witness an autobot dropship crashing into a building.
The entrance to the stellar galleries will have snipers in addition to a few enemies on ground-level. After eliminating the defenders, Megatron will blast open the locked door, and there will be a few autobots defending the path to the security pillar in the later room.