Native to the planet Cybertron, the Cybertronians fell into civil war millions of years prior to the 23rd century. Four million years ago, Cybertron was a rogue planet that drifted into the path of the Sol asteroid belt. To save the planet, Optimus Prime launched a ship that cleared a path through the rocks only to be attacked by Megatron's flagship, both ships subsequently crash landing on the nearby Earth, the crew falling into stasis lock until the 1980s. When both parties awoke, they warred for Earth's supply of energon until World War III forced them off the planet. Each faction travelled the spaceways in a Titan until a second space battle caused them to crash on Cygnus Seven.
First contact between the Cybertronian race and the United Federation of Planets occurred on stardate 5892.7. When a survey team was charting new dilithium veins on Cygnus Seven, they unknowingly found Fortress Maximus and reactivated his autonomic systems which repaired Megatron so he could investigate the alien presence. Megatron quickly revived his forces and led an attack on the colony. (TAS - Star Trek vs. Transformers comic: "Issue 2")
The colony's defences proved unable to match the Decepticons, necessitating the intervention of the USS Enterprise. In saving the colony however, the away team had wounded Optimus Prime, earning the ire of his Autobots. The Decepticons meanwhile had fled to one of the system's moons where they found Trypticon being occupied by a group of stranded Klingons and soon allied with them to destroy the humans. (TAS - Star Trek vs. Transformers comic: "Prime's Directive, Part One")
No sooner had the away team made peace with the Autobots did the Decepticons return, now allied with Kuri's force. (TAS - Star Trek vs. Transformers comic: "Issue 2") To counteract the hostiles' numerical advantage, Ratchet set up a binary bond between Maximus and Captain Kirk, allowing the Titan to heal himself by reformatting his alternate mode into a copy of the Enterprise, only to be met by Trypticon. (TAS - Star Trek vs. Transformers comic: "Issue 3")
Though Maximus was able to match Trypticon, Megatron ordered a retreat once Starscream had stolen a dilithium stockpile and flown off to conquer Qo'noS. (TAS - Star Trek vs. Transformers comic: "Issue 4")
Though Starscream managed to overpower the Klingon High Council, Megatron soon arrived and overpowered him, ordering his forces to raze the Klingon homeworld before the Autobots and Starfleet arrived. Though the Decepticons again proved the better fighters, their audio disruptor waves failed to have any effect on Klingon biology allowing a fleet of D7s to be summoned and take the invaders by surprise, defeating them.
In the aftermath, the Klingons allowed the Autobots and Starfleet to leave peacefully but on the condition that the Decepticons be left in their custody. Kirk then proceeded to invite the Autobots back to Earth only for Optimus to deny the offer, feeling that his people's destiny lied elsewhere. (TAS - Star Trek vs. Transformers comic: "Issue 5")
A race of mechanical lifeforms, the Cybertronians were an immensely durable species able to withstand the full power of a phaser with only superficial damage, multiple disruptor blasts, and even a photon torpedo detonated at close range. (TAS - Star Trek vs. Transformers comic: "Prime's Directive, Part One")
To live, Cybertronians required energon but could substitute this resource with dilithium, though it was noted to be inferior in overall effectiveness. (TAS - Star Trek vs. Transformers comics: "Issue 2", "Issue 4", "Issue 5")
Assuming they were well-fuelled and not felled in combat, a Cybertronian could theoretically live forever, leading them to be dismissive of long periods of time, regarding four million years as not particularly long. (TAS - Star Trek vs. Transformers comics: "Issue 2", "Issue 5")
They were a very diverse species. While most of their members had a humanoid profile and stood from 30 to 50 feet tall, other members might be animalistic is design, with heights ranging from 7 to 12 feet tall to giants as tall as cities, a subset of the species referred to as "Titans." Paradoxically, the members of Starscream's Seeker armada were all identical, all having scanned F-15s and having the same design for their robot modes, save their colour schemes. (TAS - Star Trek vs. Transformers comics: "Issue 2", "Issue 5")
Unlike most forms of mechanical life, the Cybertronian neural net was compatible with the Vulcan mind meld as the electrical signals of their brains functioned almost identically to the firing of neurons in organic brains. (TAS - Star Trek vs. Transformers comic: "Issue 2")
The most notable Cybertronian characteristic was the ability to transform. By scanning other machines, anything from guns, to trucks, to something as complex as a Constitution-class starship, Cybertronians could then reconfigure their body into a copy of that machine, even shedding their own natural colours if they so chose to fully mimic the machine, though any factional insignias remained on their alternate modes. Though such scans were usually done when the machine was physically present, they could make use of the machine's blueprints to gain a new alternate mode. Gaining a new alternate mode healed any injuries a Cybertronian might have. (TAS - Star Trek vs. Transformers comics: "Issue 2", "Issue 3", "Issue 5")