One of the two major factions of the Transformer race, the Cybertrons descended from the Quintessons' Consumer Goods line of robots. In the First Seibertronian War, the future Cybertrons' first leader, A3 (later named Alpha Trion) was able to deactivate the Quintesson Dark Guardians. This led to the downfall of the Transformers' masters, who were forced to abandon Seibertron.
The two lines of robots led a peaceful existence for millennia afterwards. The Cybertron leaders were entrusted with the Cybertron Matrix of Leadership, which stored the knowledge of each leader (and possibly the power of their sparks). The Cybertrons apparently founded off-world colonies in the past- however, the Cybertrons never mentioned these later, and it seems they were all lost.
Unfortunately, the peaceful times did not last- the other production line, Military Hardware, evolved into the Destrons, and gained a desire to expand and conquer. The Cybertrons resolved to prevent the Destrons from conquering other sentient life and pillaging them of their resources. As a result, the Second Seibertronian War broke out.
Many times during this war, an Cybertron ruler fell through Destron treachery, and a Destron tyrant was deposed by Cybertron forces. During these wars, the Cybertrons developed the art of transformation, reconfiguring themselves into vehicles and weapons. The advantages were two-fold- it was excellent for stealth, and it also gave the Cybertrons more battle ability. However, this advantage was soon replicated by the Destrons.
Eventually, an uneasy peace was accomplished at the end of the Second Seibertronian War. It was after this that the Destrons developed their flight technology, an ability that held many Cybertrons- such as Orion Pax- in awe. When Megatron became Destron leader, he quickly started another war, destroying the current Cybertron leader. Alpha Trion took the Matrix and kept it safe, until Orion Pax and his friends were badly wounded in one of Megatron's raids. Alpha Trion was persuaded to reconstruct them, but decided to test an experimental process on Pax and his girlfriend Ariel- he converted them into the warrior robots Convoy and Elita-One, giving Convoy the Matrix. These Cybertrons were capable of taking the Destrons on on their own terms. Thus, the Third Seibertronian War raged.
Convoy became Cybertron leader, and the Cybertrons led the war from Iacon. Unfortunately, this war was the most devastating yet, bringing the fabled Golden Age of Seibertron to an end, and severely depleting Cybertron's once-rich energy reserves.
Then, one day four million years ago, Convoy and a group of his finest warriors set out in the Ark to seek out new energy sources. After the Ark cleared a path through a meteor shower, a force of Destrons led by Megatron (aboard the Nemesis) ambushed the ship, and both groups crash-landed on the planet Earth.
With the greatest warriors on both sides lost, the war changed significantly. The Cybertrons on Cybertron broke into small groups, while the Destron forces, led by Laserwave, gained more and more dominance on the planet. The Cybertron groups became raiding parties- the most signficant such force was a group of female Cybertrons led by Elita-One and Alpha Trion. However, with energy so low, neither side could make much progress.
In 1984, the Cybertrons and Destrons on Earth were awakened, and began the war anew on Earth. Contact was made between the Seibertron and Earth Transformers, and the war was now split between two worlds. As the years passed, the situation for the Cybertrons on Earth grew steadily better, as, with a few exceptions, the people of Earth were staunch friends and allies. However, the situation on Seibertron grew worse. The Cybertrons were forced to retreat to Seibertron's two moons, while the Destrons dominated their mutual homeworld.
By 2005, the Cybertrons had built Cybertron City on Earth. Megatron led a raid on the city, during which Convoy was mortally wounded. He passed leadership on to City Commander Ultra Magnus. When the planet-eating being known as Unicron attacked, both Moonbase One and Moonbase Two were destroyed. Unicron had recreated Megatron and his dying troops into Galvatron, Cyclonus, Scourge and the Sweeps. Powerful as Unicron and his troops were, they couldn't stand up to the might of the Cybertron Matrix, which changed the young Hot Rodimus into the mighty Rodimus Convoy. Rodimus destroyed Unicron (save his head) and threw Galvatron into space.
After the defeat of Unicron, the Destrons were so weakened that the Cybertrons were able to retake their homeworld. There were five years of peace, before, in 2010, Galvatron resumed the War, and the new threat of the returning Quintessons arose. The battles continued, until the Hate Plague crisis. During that, Convoy was resurrected, replacing Rodimus Convoy as leader, and the Matrix's energies were released to end the plague. Convoy earned Galvatron's respect, earning another brief respite from war. During the next year, the Cybertrons set up a secondary base on the planet Athena.
In 2011, Galvatron attacked Seibertron with Destrons from the planet Master, resparking the war once again. Convoy died, and Rodimus Convoy was reborn, allying with Cybertrons from Master led by Fortress. However, Seibertron was destroyed, splitting the Cybertrons- some went with Rodimus to find a new homeworld, while others led by Fortress continued the battle against the Destrons.
Some time later, the Cybertrons had largely withdrawn from Earth, leaving only a secret force led by Metalhawk to protect the Earth. This group found itself facing new Destrons led by Black Zarak and Devil Z. Although the Destrons were defeated again, the Cybertrons took measures to protect the humans from further attack, helping them set up a defensive force based on Planet V and Earth's moon. The Cybertrons continued to fight the Destrons across the universe, including battles against Deathsaurus, Violenjiger and Super Megatron.
Eventually, the Destrons were finally defeated. During the next 300 years of peace, the Cybertrons settled a new Seibertron (presumably selected by Rodimus Convoy) and downgraded in size. The Convoy Council was formed to lead them. Cybertrons continued to explore the universe, only facing small threats from a Destron faction known as the True Path. The last great threat the Cybertrons faced was a resurrected Unicron, defeated thanks to Big Convoy.