The Borg are a race of cybernetically enhanced humanoids from the Star Trek franchise. First appearing in The Next Generation, they quickly established themselves as the Federation's most powerful enemy, determined to conquer and assimilate humanity into their collective. The Borg are actually made up of individuals from multiple species who have all been forced to undergo cybernetic modification, their bodies augmented with machinery and their minds combined into a singular hive consciousness. With their individual identities erased, all Borg - commonly referred to as "drones" - behave in an emotionless, robotic manner, compelled to serve the will of the hive mind.
In battle, Borg drones act much like classic horror zombies, relentlessly walking toward their enemies without any regard for their own safety. As such, they often walk straight into the line of fire which can result in a number of deaths, but again, like zombies, the Borg can quickly overwhelm enemies with their sheer numbers. Worse still, the Borg are capable of adapting to any of the various energy-based weapons common throughout the Star Trek universe, so a weapon's effectiveness against them is only temporary. After only losing one or two drones to a particular weapon, the Borg produce energy shields that absorb the impacts of said weapon. Another trait that the Borg share with zombies is that they can increase their own numbers via their victims. Whereas zombies infect people by biting them, the Borg will grab victims and inject them with nanoprobes that will rewrite the victim's DNA and create bio-mechanical implants that will convert the victim into a new drone.
As unstoppable as they may seem, the Borg have always been defeated in all their battles with the Federation. This is usually not the result of straight-forward combat but characters coming up with unconventional means of killing the Borg made possible by the circumstances of the encounter.