Michael Myers (original)

"I met him, fifteen years ago. I was told there was nothing left. No reason, no conscience, no understanding; even the most rudimentary sense of life or death, good or evil, right or wrong. I met this six year old child with this blank, pale, emotionless face, and the blackest eyes; the devil's eyes. I spent eight years trying to reach him, and then another seven trying to keep him locked up because I realized what was living behind that boy's eyes was purely and simply…evil."

- Sam Loomis

Michael Myers is the main antagonist in the 1978 horror film Halloween. He is a white masked serial killer and he is Laurie Strode's brother. Michael does not talk. He is extremely difficult, if not impossible, to kill. In this way, as well as his killing methods, he is similar to Jason Voorhees (also because he wears a mask). Unlike Jason, however, Michael kills dogs, and is not undead.

Halloween
When he was six years old, Michael Myers killed his older sister Judith, and was sent to Smith's Grove Asylum. His psychiatrist, Dr. Sam Loomis, spent eight years trying to reach him, and when he realized that he was pure evil, spent seven more trying to keep him locked away. Just as he was about to be permanently locked up, on Halloween Eve, Michael stole a Smith's Grove car and drove back to Haddonfield.

Michael stalked his other sister Laurie Strode, and tried to kill her. In the process he killed Annie, Lynda, and Bob. He received some injuries from Laurie before Dr. Loomis shot him six times, causing him to fall out the window. Unfortunately, he survived.

Halloween II
Michael continued trying to kill Laurie that night and killed many more victims, most of them at Haddonfield Memorial Hospital, but was eventually shot in the eyes by Laurie, and set on fire by Dr. Loomis, who activated several flammable gas tanks and turned on a lighter, causing an explosion that set Michael on fire and supposedly burned him to death.

From here, the series split into two timelines.

4-6 Timeline
Though it was officially stated that Michael was killed, Halloween III (which featured witchcraft and mad scientists with Conal Cochran as the main villain) received many complaints, so Michael's death was retconned and he returned in the fourth movie.

Halloween 4:The Return of Michael Myers
Michael survived the fire and was placed in a coma for several years, during which Laurie was killed in a car crash. As he was being transferred back to Smith's Grove, he heard Laurie had a daughter, Jamie Lloyd, that mean Jamie is Michael's niece, so he killed everyone in the ambulance and stalked Jamie, trying to kill her. He killed several of Sheriff Ben Meeker's cops in the process, as well as an angry mob led by Earl. Eventually he was shot by Sheriff Meeker and his troops, sending him falling down an abandoned mine shaft.

Halloween 5:The Revenge of Michael Myers
Michael survived the fall and escaped into the river as one of Meeker's troops threw dynamite down the shaft. He ended up at a hermit's house where he went into a coma until the next Halloween. He killed the hermit, causing Jamie to have a reaction that resembles a seizure each time Michael kills someone. He returned to Haddonfield and killed several more people, including Jamie's foster sister Rachel, and the new dog, Max. At one point, he listened to what Dr. Loomis had to say, and at another, he temporarily stopped his rampage of terror when Jamie addressed him as "uncle". Eventually Dr. Loomis beat him with a wooden plank and trapped him in a net, where he was locked up. Meeker planned to have him transferred to a high security cell for the rest of his life, but before he could, he and his police force were killed by Dr. Terence Wynn, who then set Michael free.

Halloween:The Curse of Michael Myers
Michael finally killed Jamie several years later, impaling her on a corn thresher, but earlier she had a baby which was also his by force conception, whom Michael could not find. Tommy Doyle, whom Laurie was babysitting in the first movie, found the baby and named him Stephen. He also discovered the truth behind Michael's motives: he is part of the Thorn Cult, with the Curse of Thorn (explaining his invulnerability), and must kill every member of his family as a sacrifice. After killing several more people, Michael eventually got tired of being used by Dr. Wynn, so he killed him and all the cult members (though some speculate Wynn survived, as his death was never shown onscreen). As he tried to kill Danny and Stephen, he was injected by Tommy with corrosive chemical and beaten with a metal pole (the chemical was seen gushing from the eyeholes of the mask).

What became of Michael afterwards is unknown; when Dr. Loomis returns, his mask was left on the floor, and we hear Loomis scream offscreen. The two most likely speculations are that either he killed Loomis, or else left (leaving his mask for unknown reasons), and Loomis saw he was gone.

Halloween H20: Twenty Years Later
Michael was not heard from since he was set on fire in Halloween II, but returned twenty years later and attacked Laurie. He was seemingly decapitated by her.

Halloween: Resurrection
However, he was not decapitated; he forcibly switched with a paramedic, who was killed instead. After killing Laurie, Michael found several people filming a reality show at his house. One of them, Sara, electrocuted him, but he survived. What becomes of him afterwards is unknown.

In other media
Michael appeared in the Robot Chicken episode That Hurts Me, as one of the two house guests of Big Brother on the chopping block (the other being Ghostface). He was pulling the pins out of Pinhead's head. He played charades with Jason Voorhees and Leatherface. When asked to give a speech on why he should stay, Michael, unable to talk, stabbed Freddy Krueger (which did no damage but annoyed him), and he was evicted. Afterward, he revealed himself as Mike Myers and killed the host.

In what can be considered the most credible fan video ever (given that Tom Kane, a professional voice actor who voiced Dr. Loomis in H20), Michael appeared in Chris .R. Notarile's fan video The Last Halloween, where Michael, at age 60, had finished killing any remaining relatives (could apply to either timeline) and was killed from the rage inside him. He also appeared in Notarile's video The Nightmare Ends on Halloween where Freddy tried to get him to spread fear (like Jason did), and fought him in the dream world. Michael, Jason, and Leatherface tear him apart at Pinhead's request.

Michael also appeared in the spoof movie Stan Helsing. He looks slightly different and is renamed Michael Crier. In the end, Stan defeats him by pulling on his mask, and he is eaten by a dog along with Jason (who is renamed Mason).