You got your science fiction in my horror! You got your horror in my science fiction! Truly a classic, and the iconic horror-SF hybrid. I actually like Aliens a lot more, but that’s not a horror movie, just a military SF movie inspired by a horror movie: this horror movie. And as a horror movie, it’s solid.
You all know the story. A spaceship sets down on an isolated planet to answer a rescue beacon. Crew investigates; finds alien spacecraft piloted by dead giant elephant people. Crew member is attacked by strange egg (rather, contents thereof) and ship beats it the hell out of there. And that’s when the alien spawn bursts its way out of said red shirt’s chest, running amok, killing people, and fouling all attempts to contain it. As a cargo ship, there’s no means to kill the thing; on top of which, a traitorous cyborg is under orders to bring it back to earth at all costs.
At the very least, that H.R. Giger alien design is creepy as all get out. It’s a good example of the change in perspective about aliens: in the B-movie age, they were always humanoid, or “changed form” or abducted or did whatever to become humans, matching the ethnicity of whoever was making the B-movie. Alien was different: it’s an actual alien. And a damn scary one at that. Acid blood, a second mouth, and the design follows Giger’s weird fascination with streamlined form and sexuality.
It’s also worth noting its female protagonist/hero, something that hasn’t been replicated effectively since. Sure, there are a lot of female heroes, and a lot of female protagonists, but few blend those roles simultaneously to become capable badasses like Ellen Ripley. Science fiction has a long, bad habit of placing its female characters in subaltern roles: the chick who gets dragged off by Ming the Merciless, or who harries our hero with her stupidity/romantic subplots/comic hijinks/whatever. (I mean, at least crime novels get femme fatales who can handle guns and wrap men around their fingers.) Alien made some waves by having its protagonist be a capable action hero to stand out from the crowd; the plan worked, and helped launch the careers of the Alien franchise and Sigourney Weaver’s career.
Why is it scary?
The alien is unstoppable and nigh unkillable. The setting is a tight, compacted spaceship laden with ducts and tunnels, floating in the void of space, light years away from help. The corporation views the crew only as meat bags to store their potential new weapon in.
Yeah, there’s a lot of horror in here. Maybe it’s just me, but space should have this psychological horror to it to begin with, even if it’s the subdued loneliness of Moon and not void-induced paranoia of Pandorum. Space is a lot like being underwater: the last place I’d want to be stuck with a killer [insert noun here], because one crack and the walls cave in to crush you. Especially one that bleeds acid, which can melt holes in your ship. And you have no means of defending yourself, no where to go, and nobody to call for help.