Metroplex is an Autobot titan whose alt-mode is a city itself. In other words, don't make him angry.
Fall of Cybertron
Metroplex responds to Optimus Prime's desperation during last ditch effort to repel the Decepticon siege of Iacon and leads the Autobot Leader to his spark chamber to be activated. He is a towering Autobot that is covered from head to toe in heavy artillery weaponry.
He is the last line of defense for the Autobots and will respond only to the commands of the last Prime. This also allows Optimus to sync with Metroplex's targeting systems and mark targets for Metroplex to destroy. Examples include Metroplex launching artillery strikes from his shoulders, swatting dropships out of the air, or even wading into the battlefield and stepping on the poor Decepticons.
In the mission "Metroplex Heeds the Call", Metroplex is called on to destroy the three Decepticon Warp Cannons that are firing on the Ark. Along the way Metroplex aids Optimus in many ways from stomping on Decepticon troops firing on Optimus, forming a bridge with his hand for Optimus to cross, and punching a trio of Decepticon Leapers that had cornered Optimus.
As Optimus makes his way through the ruins of Iacon, he and Metroplex are able to destroy two of the three Warp Cannons firing on the Ark. The third and final warp cannon is able to fire off a charged shot that temporarily incapacitates Metroplex. This forces Optimus to try and disable the cannon manually which ends in Optimus walking into a Decepticon ambush lead by Starscream.
Optimus is then brought before Megatron. But before Optimus can be executed, Metroplex, now back online, interferes and tears the roof off of the building that Megatron is in and proceeds to pound the Decepticon Leader into oblivion.
With the siege of Iacon broken, the Autobots venture out in order to gather more energon to power the Ark. Metroplex stays behind to protect it.
After the final reserves of energon on the planet are taken from the Autobots, Metroplex offers his own energy in order to fuel the Ark. As the Ark lifts off from Cybertron, Metroplex makes one last statement "'Til all are one."
Rescue Bots Academy
Metroplex was featured on a card in the Heroes of Cybertron trading card series which Wedge owned.