When you reach the bridge, you will see a short cutscene of the Combaticons transforming in preparation to bring the supports down. The artillery fire won't be enough to bust through the bridge's heavy armor plating, though, meaning that you will have to transform into your vehicle form and head into the fray to lower the shields. Boost in your jet form over to the anti-air and transform into your helicopter form. Hit Y to switch weapons and dump explosives onto the Marauder. You will have to use a sort of hit and run attack pattern here to deal with the Marauder, because its anti-air capabilities can down you very easily. You can pick up an Orbital Beacon power up from the roof of one of the large spires next to the Marauder, which will boost your damage temporarily. Make use of this to blast the Marauder and a few of the footsoldiers if possible.
When you have finished off the Marauder, you will probably need to restock on health and ammo. Use the platform in the center and the lower section of the platform, which is walled in from most sides and provides better protection from more angles, to grab the health and ammo you need, and then hover around the platform and blast the enemies with your explosives to wipe them out quickly. You should be able to easily pick off the enemies from the sky. When they are all gone, drop down to the central platform and pull the switch to open up the armor on the first bridge support. Rush over to the boase of the bridge support, and loot the chest there for ammo.
You will now have to attack a second bridge support, which iwll be more heavily defended than the first. Transform back into your vehicle form and jet over to the opposite side of the bridge. At this checkpoint you will have to deal with two Marauders and a few more footsoldiers. Use the series of catwalks for cover when taking out the Marauders. You will have to shoot away a few of the soldiers first, and then use the pillars and supports to divert artillery fire while shooting back with explosives.
Note that there is health littered about the horizontal walkway, one on the left and one on the right. Heal yourself and refill your ammo, and after the lengthy process of defeating the Marauders head down and flip the switch to open up the armor on this second bridge support. Even after blasting this bridge support, you will still have another to go. This will be perhaps the most challenging, as two dedicated anti-air turrets, one to the left of the support and one to the right of it, will guard it along with a bast array of enemies on the ground. Blast the anti-air guns with your explosives, and head down to the ground if you need to refill your ammo. After defeating the enemies outside of the support, you will have to drop down into the bridge itself so that you can open it up from the inside.
Transform back to your robot form, collect the weapons, ammo and currency at the end of the drop, and Proceed ahead into the level. Enemies will attack you from both above and the ground level. Use the Riot Cannon to one hit blast the enemies as they charge you. When everyone is gone, take the elevator down to the lower floor, use the shop to the right if you need it, and sprint over to the left. Transform back to your vehicle form and boost down the hall and into the blue corridor ahead. Dodge the beams and drop down into the next room, turning back to robot form. Pull the switch to open up the door. This will lower the walls on all sides of you, leaving you vulnerable from all sides at once.
There is a sparse amount of ammo and health on your platform, but you will not want to stay on this central platform for long, as everyone will be focusing their fire on it. Boost off of the platform as soon as you can. Pick one side of the arena and start from there, using the crates and walls for cover. Grab new weapons from the Armory Reactors if you need to, and be sure to keep away from the Shotgunners when they jump up to the catwalks to meet you. Slowly sweep from one side of the room to the other, killing everything you find along the way. Be careful as you go, as there will be a lot of enemies in this room and you will need to take your time in killing them.
When all of the enemies are dead, flip the switch in the center of the room to bring the cover up ahead. A large Autobot enemy will rise in the lift ahead of you. Dodge around the pillars, using them and the adjacent crates for cover from the large minigun. There's no special strategy really for defeating these big guys. Instead, hit the Autobot as much as you can, especially when it is reloading, and just try to stay out of its line of fire. Eventually, the Autobot will spawn drones to shield it. At this point, you will have to eliminate the drones in order to bring down the shield. With the giant Autobot dead, pull the switch to start blowing the bridge. Transform to your vehicle form and boost out through the blue corridor ahead. You will have a limited time to escape, but you shouldn't have a problem here. Fly out and into the open air, ending the mission.
