Transmetal

Transmetals are a subspecies of mutated bestial Triple Changer-like Cybertronians from the planet Cybertron.

Anatomy
Transmetals share a similar biology to other bestial Cybertronians, except their superstructures have been mutated into a mode-based inversion of organic and mechanical composition. Technically speaking, a Transmetal's beast mode is mostly mechanical while their robot mode bears many organic elements.

Powers and abilities
Transmetals share many of the same abilities as other Cybertronians, especially Triple Changers. This trait is due to possessing "mobility" modes, which is essentially the beast mode with some vehicular additions.

Transmetals are immune to the effects of Vok Metal Hunter, which would debilitate a normal Cybertronian. According to Tarantulas, this is because Transmetals are closer to being Vok themselves.

Transmetals appear to have temporary resistance to the full effects of Megatron's transformation virus.

Weaknesses
Transmetals share many of the same weaknesses as other Cybertronians.

Transmetals can be reverted to their original state by Megatron's transformation virus.

Culture and society
Transmetals appear to share the same culture as other Cybertronians.

Fuzors are considered to be Transmetals to an extent, as they are immune to the Vok Metal Hunter yet vulerable to the transformation virus.

Primax 496.22 Alpha
The energies of the quantum surge produced as a result of the Vok Planet Buster's destruction caused a number of Maximals and Predacons to be reformatted into Transmetals.

Cybertronians such as Rhinox, Dinobot, and Waspinator were not reformatted into Transmetals due to being shielded from the surge's effects by CR chambers. Similarly, Cybertronians "born" from protoforms found on prehistoric Earth were unaffected by the surge.

Primax 399.19 Kappa
Unicron's minion Reptilion was a Transmetal Decepticon.

Primax 700.12-N4 Kappa
Due to Megatron's temporal manipulations, several more Cybertronians including Waspinator and Airazor gained new Transmetal forms from the quantum surge.

Other notable Transmetals found in this universe include Terrorsaur, who survived falling into lava during the surge; Starscream, who was reborn in a new body based off Waspinator's; and Megatron X, a clone of Megatron created by agents of the Vok.

Primax 206.15 Gamma
Predacon Scavenger emerged from his stasis pod as a Transmetal, despite only existing as a protoform beforehand.

Legends World
During a battle at Autobot Headquarters, Decepticon leader Megatron took a blow from Autobot leader Optimus Prime so powerful it damaged his internal stability regulators. This allowed Megatron to access a cache of quantum surge energy that had been stored in his body for millions of years, reformatting himself into a nigh-invulnerable Transmetal.

Megatron subsequently left the Autobots to take revenge on the treacherous Slugslinger, promising to show them his newfound power soon enough.

Aurex 1104.30-JH Zeta
Optimus Primal destroyed Tarantulas's shipload of Super Energon in orbit, triggering a Super Energon Transwarp Explosion which reformatted several Cybertronians into Transmetals.

One such Cybertronian was Ghashteeth, a Mini-Con affiliated with the Predacons. Upon his upgrade, he changed his name to Chromebite.

Origins

 * Initial Transmetal toys were designed with only melee weapons, rather than the guns seen in the Beast Wars animated series. As a result, Mainframe Entertainment was forced to come up with creative solutions to give these characters ranged weapons without diminishing their toy accuracy. For example:
 * Tarantulas's handheld buzzsaw functioned like a gun and the green markings on his shoulders were depicted as missile ports.
 * Megatron's pincer/whip/flail/"whiplash cutlass" thing (his beast mode's tail) gained the ability to stiffen and fire like a cannon while his dinosaur arm kibble moved forward to function as shoulder guns.
 * Cheetor's hands were capable of firing energy blasts, usually when placed together and thus temporarily making the halves of his beast-mode head whole, with the zaps emanating from its mouth (a pose impossible to achieve with the figure without unhinging the shoulders from the sides).
 * Even more elaborate was the functional reconceptualization of Optimus Primal's toy, whose hoverboard thruster/mace launcher was used as a laser pistol. Not content with this rather puny-looking firearm, some clever cove at Mainframe noticed that his shoulder-pad and mace-stowing bracket thing could be flipped over his head (a function of his transformation) and improperly positioned in such a way that the long handles of his dual maces pointed outwards like gun barrels. With the shoulder-pads positioned over his outstretched fists like trigger-guards, the whole device was re-imagined as something resembling two machine guns mounted on a Steadicam harness.
 * The only exception to these exotic re-imaginings was Rattrap, who used his tail/whip/spear as intended but also retained his pre-Transmetal gun (with was recolored to suit his new color scheme), despite the fact that the toy did not.
 * As an odd point of comparison, the later Transmetal Optimal Optimus was packaged with a rifle, which he never used in the show. Presumably someone decided that his large chest cannons were enough (although they also made them retractable, unlike the toy).