A force field, sometimes called an energy shield, is a device used for purposes of defending an object or location, or serving as a means of imprisonment.
The Autobot Trailbreaker was equipped with a force field generator. He often used it to move things away, such as floods. After being attacked by the Rainmakers, Trailbreaker projected a force field to allow the Autobots time to repair themselves from the damages suffered from acid rain.
Defensor was also equipped with a forcefield, but his had the bad habit of running out of juice after a very short amount of time, causing it to deactivate. This rendered its usefulness debatable.
After being on Earth for some time, Rhinox developed a shield system as part of Sentinel's security systems. The shield could stand up to a heavy amount of punishment, though at times it inevitably failed. After the Axalon sank into the river near it, the Maximals attempted to salvage Sentinel, but the Predacons managed to steal the control system and installed it in the Darksyde, simultaneously managing to bolster their own defenses and putting the Maximals on a defensive footing for the remainder of the Beast Wars.
After moving into Mount St. Hilary, the Maximals attempted to use Teletraan I to power their shields, but Autobot technology and Maximal technology were too different to make a compatible system, leading to the aforementioned salvage attempt.
Megatron installed powerful shields aboard the Grand Mal, which were the only defense the Maximals could activate when the Vehicons attempted to take the vessel back. The shields, however, cut Botanica off from Cybertron's organic core. To save her, Rattrap launched in an escape pod containing a shield emitter which mimiced the Grand Mal's own shield harmonics. Megatron found the emitter, and transmitted the harmonics to Obsidian, whose forces shot the Grand Mal out from the sky.