The Age of Rust (also known as the Rust Age) was one of the designated periods of Cybertronian history recorded in the Covenant of Primus. It was marked by social and societal atrophy, as a demoralized Cybertron sought to recover from the failure of the Golden Age.
The Golden Age of Cybertron came to an abrupt conclusion when the colonies became infected with a Rust Plague. Possibly a deliberate attack by unknown parties, the plague was incredibly virulent and apparently incurable. Sentinel Zeta Prime and the council of thirteen on Cybertron made the heavy decision to destroy the Space Bridge network for maximum quarantine, cutting off the colonies from Cybertron and abandoning them to their fate to prevent the plague from spreading to the homeworld.
By rust they fell and to rust they came. The global optimism brought about by the space exploration and colony programs was irrevocably lost. The people of Cybertron felt they no longer had anything to strive for, and merely went through the motions of existence. This malaise only intensified when Nameless bots began emerging from the Well of All Sparks en masse, just as they had during the Age of Wrath. The general consensus was that these new bots saw existence as too pointless to even bother choosing a name, or have things to look forward to. They merely went about their appointed role in life, no more or less.
Sentinel Zeta Prime managed to hold on to power during the Age of Rust, but accomplished little else. The rest of his council was too gun-shy and lacked the drive to begin new social programs or expeditions to reignite the people's spirit. The one exception was councilor Soundwave, who abandoned the council in disgust for their failures.
The one growing "industry" on Cybertron during the age was gladiator combat, ruthless games of merciless combat and bloodsport arising from Kaon. Either vicariously or in the gladiator pit themselves, Cybertronians found themselves momentarily alive again as part of the ritual combat. It was in these games that a miner designated D-16 claimed the title of Megatronus, fallen of the Primes, before the exuberant crowds shortened his name to Megatron.
Megatron was a visionary as well as a warrior, and began addressing his audience of fans about the possibility of social change, even revolution. Indeed, Megatron ultimately brought about the end of the Age of Rust, but not how he expected. Megatron and his allies received an audience before Sentinel and the council to address their concerns, but the council sidestepped Megatron and presented the title of Prime to one of his less extreme advisors, the archivist Orion Pax. As Pax rose to become Optimus Prime, Megatron rejected his former friend and began open warfare in the streets of Cybertron. These two leaders and their factions, the Autobots and Decepticons, began the Great War that shook the rust from Cybertron's society, for good or ill.