kuzzy: Transmetals appeared in Beast Wars in the 1998 line and appeared in the show in Season 2. Transmetals are Transformers which have robotic looking beast modes and bestial looking robot modes (except for Optimal Optimus and Ravage who are wholly mechanical in all modes). They also have intermediate vehicle modes (an intermediate mode is a kind of "half mode" - it's not a full proper alt mode, they're basically modifications of their beast mdoes). In Hasbro markets Transmetals were very popular but in Japan (where the Transmetal/Fuzor line was known as "Beast Wars Metals" it didn't enjoy the same success as the Japanese fandom criticised the Metals line as being unconvincing robots in disguise. The Japanese BW line reverted back to more realistic looking beast modes in the 1999 line (aka "Beast Wars Neo").

Transmetals TV commercial
Optimus Primal/Optimal Optimus in action

As far as the fiction is concerned, Transmetals were created when some Beast Wars Transformers were 'mutated' by the quantum surge that was resultant from the destruction of the Vok's lunar planet-buster (except for Optimal Optimus & Ravage). Transmetals and Fuzors are also invisible to detection from Vok technology (probably because they were irradiated by Vok energies rendering them "friendly" to their machines).

Getting back to the toys, there have been some different variations of Transmetals. There are numerous Fox! Kids and Wal-Mart exclusive variants, which are really just repaints. Most of them aren't terribly interesting unless you're a collector of variants. The only one of those variants I'd recommend would be Wal-Mart Transmetal Rattrap, which is meant to be Transmetal Packrat, but Hasbro doesn't have the rights to the name Packrat so they called it Rattrap instead. But official canon has retconned that figure as Transmetal Packrat.
Transmetal Packrat from "The Wreckers"

The Japanese Metals versions also feature more show-like colours and most noticeably in Megatron, better quality plastic. Transmetal Megatron notoriously suffers from poor quality plastic which makes the toy easily susceptible to breakage. The Japanese version has much better quality plastic and also nicer colours too.

Ravage is only available through the Japanese Metals line (where he's known by his Japanese name "Jaguar").

I personally really like Transmetals and highly recommend them to collectors. If you're interested in completing all toys who appear in the Canadian TV show then here's the list:

Maximals
+ Airazor
+ Blackarachnia (Transmetal 2)
+ Cheetor
+ Cheetor (Transmetal)
+ Cheetor (Transmetal 2)
+ Depth Charge
+ Dinobot (you have the reissue :))
+ Optimus Primal (Ultra gorilla)
+ Optimus Primal (Transmetal)
+ Optimus Primal (Optimal Optimus)
+ Rattrap
+ Rattrap (Transmetal)
+ Rhinox
+ Silverbolt (Fuzor)
+ Tigatron
+ Tigerhawk


Predacons
+ Cicadacon*
+ Dinobot (Transmetal 2)
+ Inferno
+ Megatron (Ultra T-Rex)
+ Megatron (Transmetal)
+ Megatron (Transmetal 2)
+ Ram Horn*
+ Rampage
+ Ravage**
+ Scorponok
+ Sea Clamp*
+ Tarantulas
+ Tarantulas (Transmetal 2)
+ Terrorsaur
+ Waspinator


Unaligned
+ Transmutate (build-a-figure, parts were sold with Hasbro's BW reissues)


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*Tripredacus only appears in the show in their Cybertron form and look very different from their toys.
**aka Beast Wars Metals X-9 Jaguar