The Guards were a type of tank-treaded robot warrior used by Shockwave. They did not speak or appear able to transform, and were typically overseen by the Head Guard (at least until he was incinerated).
The Transformers cartoon
When the Dinobots arrived on Cybertron through the Space Bridge, a large battle ensued in Decepticon Headquarters between the stompin' cyber-saurians and Shockwave's guard robots. Despite destroying many of them, the Dinobots, except for Swoop, were overwhelmed and captured.
Later, Spike Witwicky and Carly arrived on Cybertron, escaped Shockwave's grasp, and met up with Swoop. A group of guards accompanied the Head Guard in locating and capturing them. The prisoners were then sent to the Cybertonium Pit, where they were watched until a fight broke out between Spike and Grimlock. Lowering the force-field in order to remove the humans, the guards were attacked by the Dinobots, who made short work of them.