Transmetal

Transmetals are a subspecies of mutated animalistic Cybertronians from the planet Cybertron.

Anatomy
Transmetals share a similar biology to other bestial Cybertronians, except their superstructures have been mutated by an anomaly called a quantum surge. The most obvious effect is a mode-based inversion of organic and mechanical composition. 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.

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).