Metroplex TFP

"Metroplex heeds the call of the last Prime."

- Metroplex after being summoned by Optimus

Metroplex is a gigantic Autobot whose alternate mode is a city. A more than capable arsenal in the Autobot ranks, Metroplex doesn't care for his own safety and is more than willing to sacrifice anything if it means securing the victory for his comrades in the war. He has tremendous power, is loaded with rockets and isn't afraid to crush Decepticon leaders with his fist. Don't piss him off.

Biography
The exact circumstances of Metroplex's creation are unknown, but given that he answers to Optimus Prime alone, it is believed the Primes created him out of their city. Eventually he ended up in stasis lock where Iacon would be built, unknowingly becoming its center.

Transformers: Fall of Cybertron
Metroplex had been lying dormant in what would become Autobot City for thousands of years, and inadvertently became a part of the battlefield when Megatron attacked the Ark. After pulling a switch or two, Autobot leader Optimus Prime observed the interior of Metroplex constantly shifting and transforming to accommodate him. After using a turret to help fight the Decepticons, Optimus found himself herded to a mysterious bright light by the shifting interior. Sensing a Cybertronian presence, Optimus desperately ordered the entity to help the Autobots in their time of need. After a final switch, an entire city began to transform into an immense, powerful Autobot—Metroplex, who had heeded the call of the Last Prime.

Metroplex's presence on the battlefield proved invaluable to the struggling Autobots. The titan easily wiped out much of the Decepticon army, including the deadliest of foes such as Marauders. Metroplex would launch a devastating air strike on whatever target Optimus marked for destruction, and the colossus was able to wipe out Megatron's equally massive guns that were giving the Autobots a hard time. However, just as he was to destroy the last of the towers, it shot Metroplex point blank in the chest, felling the mighty giant. Fearing for the worst, Optimus pushed on, but was captured by the Decepticons, and brought to Megatron, who mocked and berated the helpless Autobot leader.

However, the villain gloated too much, and Metroplex revealed his survival by ominously approaching from the back of Megatron's base. After Metroplex breached the walls of the base, the Decepticons were quick to back away from the huge threat, but Megatron ordered them to stand their ground. It was at this point that Metroplex had enough of the tyrant, and crushed him several times with his enormous fist, killing Megatron to the shock of the Decepticons, who were soon led in a retreat by Starscream. Unfortunately, the energon used to fuel Metroplex and the Autobots' defense of Autobot City drained their supply, preventing the Ark from being launched. Still, Optimus was glad to have an ally like Metroplex on their side.

Days later, after the Autobots located another source of energon—only for it to be halved thanks to the Decepticons—Metroplex offered to sacrifice his life, donating the energon inside him to give the Ark enough juice to launch. Optimus protested, but Metroplex had made his choice. Connecting his Spark to the Ark's fuel tanks, there was enough energon to launch the ship. The heroic titan collapsed for a final time, but was happy to see the Autobots finally leaving Cybertron, and in his dying moments, Metroplex's last words were, "'Til all are one."

Optimus Prime sadly swore that Metroplex's sacrifice would not be in vain.

Personality and Traits
Metroplex has shown undying loyalty to Optimus Prime and a love for Cybertron. Despite this compassionate traits, he is shown to have an extremely short temper, smashing several Decepticons, whose firepower could not affect him and murdering Megatron for one shot to the chest.

Behind the Scenes

 * Metroplex first appeared in the G1 cartoon as a city in Transformers:The Movie & as a robot in The Five Faces of Darkness mini-series. Oddly for an '80s cartoon, he was euthanized to prevent him from being infected by the Hate Plague. While he firmly established as an artificially created life-form in that continuity, his origins are left ambiguous in the Aligned continuity family.

Trivia

 * Metroplex is technically the largest playable character in Fall of Cybertron video game. Bruticus is a distant second and Grimlock close behind.