The Zombies are recurring enemies introduced in Metal Slug 3.
In Metal Slug 3, zombies were once regular people, Rebel soldiers and researchers that are transformed by the power of the Monoeye UFO. In Metal Slug 4, the boss of mission 4, Big John, is used by the Amadeus Syndicate to turn everyone in the area into zombies.
Zombies are slow-moving, clumsy enemies, but they can zombify any human, both NPCs and players, almost instantly with their infectious fluids. They are significantly more durable than ordinary humans, with even the weakest able to withstand several rounds of fire before destruction. Fortunately, they are slow-witted, easy to outmaneuver, and often trip when fired at. POWs are not infected by any type of zombies' attacks.
If the player is hit by a zombie attack, they transform into a zombie. As a zombie, the player's character moves much slower, jumps much lower, cannot crouch, and is restricted to their default pistol weapon. Also, an attack from an enemy zombie or the level boss will kill a zombified player. On the other hand, the advantages of zombified player are that the player is immune to nearly all attacks from the Rebels, and the player's bombs are replaced with a deadly wave of bloody vomit which covers nearly the entire screen. Enemies killed using the blood wave don't give any bonus points from it. Zombified players can transform back to human form by obtaining a first-aid kit.
Infected Survivors make up most of the zombie horde. Slow and individually weak, they can quickly gang up and overwhelm the player. Common zombies trip over the most often.
Note: All common zombies act the same, the only difference is their health, speed and toughness.
|Man: This one will vomit infectious fluid into his cupped hands, and then hurl it at his target.|
|Woman: This zombie will vomit infectious fluid directly at her target.|
|Young Man: This zombie squirts a blob of infectious fluid from his brain cavity by squeezing his head. He also moves faster than the other common zombies, most likely due to his young age.
In Metal Slug Attack, he is introduced as an Invader-affiliated zombie, with a parasitic larva infecting him. Along with the attack used in the original series, he can also squirt larvae at enemies, who burn enemies on impact.
|Fat Man: This one can launch infectious fluid at his target by opening his rib cage. He has greater resistance with bullets and grenades compared to other common zombies.
In Metal Slug Attack, there is a variant sporting a red coat that is much more durable although prone to tripping often.
|Scientist: This zombie uses his intestine as a kind of "hose" in an attempt to spray zombifying liquid on the player. When killed, a first-aid kit will be left behind. He has slightly less health than the other common zombies.|
Uncommon zombies are more dangerous and have unique attributes. They are typically found in specific areas of the mission.
|Rebel Soldier: This zombie is faster than the others, likely because of their military conditioning. As with the other zombies, they are far more durable than ordinary Rebels, requiring nearly a dozen bullets to take it down. They are also unique in that they leap at the player rather than attacking from a distance and explode upon contact with the ground or the player. They also do not trip as often as the other zombies.
In Metal Slug Attack, there are zombified Blaze Brigade soldiers who act similarly to their standard counterparts, except they can jump twice before exploding, and each explosion generates fireballs that land in the nearby area.
|Tar Man: The most dangerous of the bunch. This one is just slightly slower than the Rebels. When in front of their target, they attack by throwing a spread of goo. If they are on a platform directly above their target, they will drop down in an attempt to land on their target in a similar manner to the Rebels. This zombie rarely trips.|
|Jane Doe: A female Rebel Infantry that has been reawakened as a zombie. Donning a nurse outfit, she uses her pheromones to control the undead. Any units she lands the final blow with are locked and cannot be deployed again for a short time. Jane Doe never trips.|
- Zombies are possibly based on the classic "Romero" zombies as seen in films such as Dawn of the Dead. Interestingly, unlike the typical type of zombies most people are familiar with, zombies in the Metal Slug series do not attack by biting.
- If a zombified player gets hit in mid-air by an enemy zombie or by the boss, the player will explode just like how the other zombies do when killed.
- While generic zombies are associated with the Martians due to the Monoeyes accidentally creating them in the original series, in Metal Slug Attack, the young male zombie is affiliated with the Invaders.