There are two major 'genres' of zombie films, "apocalyptic" ones and "necromancer" stories.
In the most popular type of zombie film, the recently deceased start re-animating and attacking the living. The phenomenon tends to spread and become more serious over time. These are the "apocalyptic" zombie films, such as:
George Romero's of the Dead zombie films are by far the most important and 'purist' of the zombie films. They are: Night of the Living Dead, Dawn of the Dead and Day of the Dead, followed by a remake of Dawn of the Dead and finally Land of the Dead. This series is sombre, progressive and strife-orientated, with a tendency towards classy b-movie style.
Dan O'Bannon's Return of the Living Dead series are a comical and fun progression from Romero's Night of the Living Dead, and zombies follow all the same rules. The main difference is that the zombies are more talkative. I am not including (for now) these films on these pages.
Older zombie films normally included a necromancer who raised up some bodies for his own purposes. Only a few modern zombie films follow this "voodoo" stereotype, and include the Reanimator films. For now, this website is only about the apocalyptic zombie films, not the necromancer ones.
Zombie films fall into two major types:
The Build-Up zombie film often starts with just one zombie, or just one small town in the middle of nowhere. This one zombie encounters the cast of the film, and eventually turns more and more people into zombies. The film expands, with state-wide or nation-wide news reports showing us that this is a growing epidemic of increasingly serious proportions. During the build-up, the cast have to fight harder and harder to stay alive, and eventually are forced to find somewhere safe and secure, where they barricade themselves in against the walking dead outside. The second half of the film then follows the second major plot: The Survivors.
The Survivors zombie film plot has a group of survivors in a secure, fortified location trying to live their lives. Largely, the zombies are kept at bay. Existential questions are asked: What is the meaning of life, what can we do in the long term, can we continue to live like this? Etc. The plot always develops that internal personality clashes or politics leads to the group breaking apart, and the result is that the security of the compound is compromised, and the zombies get in. This is frequently due to the reckless action of a dissenter in the group, who opens the doors or who tries to leave.
Mysticism and the Unexplained: Not all zombie films offer explanations of why the dead now refuse to die. Some esoteric hints are dropped, such as the subtitle to Dawn of the Dead: When hell is full, the dead will walk the Earth. This implies that the living who die are largely going to hell, but, at some point hell is full, so the souls of the dead linger on, animating their dead bodies. The living pay for the sins of their (dead) compatriots, as society as a whole has failed.
Radiation: In Night of the Living Dead the explanation is a Faustian rejection of science: Generic 'radiation' from a 'space probe' that exploded is 'increasing' throughout the film (as heard on background news reports), and this may be causing the recently dead to return to life.
A Virus: Many zombie films explain the morbid happenings as the result of a disease: Some kind of spreading infection, if caught, causes a severe cold that results in death, and the dead then return to life. It is like a possession where the 'original' person is slowly replaced by a zombie, and the final transformation occurs when they die. The rejection-of-science theme sees Night of the Living Dead attribute this to radiation, 28 Days Later attribute it to a genetically modified virus and the Return of the Living Dead series blames an evaporated poison. Only some more outlandish zombie films break from the anti-science trend, for example Braindead which attributes the disease to a natural virus resulting from a dangerous hybrid rat-monkey.
Disease and virus orientated films have the 'infection' spread from its original locale across a state, a country, or even across the world. Some films, such as the Romero of the Dead series, merely has it that for some reason that scientists cannot discover, anyone who dies returns to life (unless, presumably, they have suffered serious brain damage).
Most zombie films have the zombies hard-to-kill unless you know how. Their bodies are weak and easily damaged... but, normal damage does not kill them. They feel no pain and do not care to preserve themselves or defend themselves. Their only motivation is to attack the living. To kill zombies, in a classical zombie film, you have to:
Destroy their brain. If you destroy the nerve centres of the brain, especially the modules that control motor functions or the brain stem, you disable the zombie. Cutting its head off means that it can't control its body, and the body becomes a normal dead body.
Burn them. A burning zombie will normally become distressed, more confused than normal, and will sometimes try to pat itself out (though it can never succeed). After a while, the zombie will collapse. Fire will frequently scare zombies and keep them at bay.
Demolish them by crippling and destroying their whole body. Once a zombie is shot in the head, flaming pyres are the best place to dispose of the body. Some films have it that this destroys the virus too, otherwise the corpses can still spread infection.
There are exceptions... in 28 Days Later, zombies have more normal bodies and can be killed like a normal person. In Braindead it appears that the zombies entire nervous system is given a murderous will to kill the living: In the most strong-willed zombies, their body parts remain animated even after destruction of the head or after truncation from the torso. And in Reanimator, the injected liquid appears to give any flesh an individual will and mind. But these films stray from the zombie 'norm' of brain-based motivation, and therefore death by brain death.
Where do zombies' motivations and willpower come from? There are two general trends in zombie films:
Materialism: The brain is the source of willpower, so, a biological disease, radiation or a chemical makes changes in a person's brain, so that when they die certain parts of the brain remain active and motivate the zombie. Zombie willpower is fundamentally a result of a broken brain. This is seen in most apocalyptic zombie films and some necromancer ones.
Animism: Motivation comes from a more mystical, ethereal source. Zombies' wills are fundamentally an evil, psychic force from beyond the grave. It is animist in that in certain films containing zombies (Braindead and the Reanimator necromancer films), body parts can obtain wills of their own. This clearly disassociates willpower from coming from the brain.
Animism is unbelievable for one major reason:
“Motor functions in our nervous system are controlled centrally by organs at the base of our brain, at the top of the spine, such as the medulla and cerebellum. Orders travel from here, down the spine, to the appendages. The appendages' nerves have no system to self-rule. In other words, muscles can only be controlled in a directed way, from the brain. As a result of this, animist zombie films must somehow explain that (for example), a hand on its own has had its nerves physically rewired into a new motor control area. It becomes far too complicated and unlikely that mystical sources of willpower could ever accomplish this.”