Alien invasion: what are we really afraid of?

About 40 minutes into the new alien-invasion spectacular, Skyline, you get the big money set-piece sequence. Here gung-ho 20-something heroes Jarrod (Eric Balfour) and Terry (Donald Faison) climb out on to the helipad of the latter's apartment building to survey below them a Los Angeles wholly at the mercy of otherworldly spacecraft that are descending slowly from the skies, shooting out phosphorescent beams and decimating the unsuspecting population below. In particular, the craft ahead of Terry and Jarrod opens like an evil crustacean and sucks up into its belly, directly from the ground, the hundreds of thousands of luckless Angelenos who are caught in its path.

The shot is a winner. The bodies whirl upwards through the air. They scream, they writhe. It's like 9/11 in reverse. And in our minds we know that the movie is asking big questions about the loss of life since 9/11, and the devastating otherworldly threat that is today's global terrorism.

Similarly, in the upcoming sci-fi movie Monsters, a near-future world is depicted where the southern border of the United States is protected by a giant "security fence", separating it indelibly from the terrifying population of squid-like behemoths that now live in Mexico, aka the infected zone.

Despite the description of a quiet human romance that sputters into life throughout the movie, this is, in short, a cutting commentary on Fortress America, on US isolationism, and on the growing anti-Mexican prejudice in much of mainstream American society. For the one thing we've learned from alien invasion movies, in the 60 years since their mid-20th-century heyday, is that the aliens are rarely just aliens. Or are they?

There were, of course, alien-invasion archetypes long before the 1950s, most notably in literature with the 1898 HG Wells classic The War of the Worlds, in which Victorian England is trashed by pitiless Martians who - in a grand rhetorical coup on Wells's part - represent the pitiless imperial demeanour of the British Empire itself. And there were even a few alien appearances on screen in the pre-history of mainstream cinema too, such as the infamous lunar-based "Selenites" (men in skeleton costumes with pointy masks) in Georges Melies's A Voyage to the Moon (1902). But the alien-invasion business itself, as we know it today, didn't really take off until the so-called communist threat and the nuclear age collided in a soup of Cold War paranoia and created an hysterical drive, even a need, for tales of monumental dangers to the American way of life.

Thus, in 1951, The Day the Earth Stood Still gave us a technologically superior alien super-craft landing in Washington to warn Americans about their impending doom. In 1953's It Came from Outer Space, the aliens came to small-town Arizona and kidnapped the inhabitants, replacing them with slow-talking, unfeeling automatons (aka commies!). And in the big-screen version of The War of the Worlds, from the same year, the American public were given it with both barrels, right between the eyes - the action was transposed to California, but the message was the same: They're coming to get you!

And so it continued. Earth vs the Flying Saucers, Invasion of the Body Snatchers, The Thing from Another Planet, and so on. All movies that derive their pleasure from depicting aliens in our midst, but derive their power from the unspoken suggestion that the aliens aren't really aliens at all, but merely two chromosomes away from crazed, homicidal communists.

This affinity for metaphor has, of course, stuck firmly to the alien invasion movie ever since. And while the subject that the aliens refer to has shifted constantly over time, their own status as metaphorical vessels has never once been in question. Typically in the 1970s-era of Close Encounters of the Third Kind and Starman, the aliens were benign mirrors that asked us to look within ourselves for our lost humanity (see also the brand leader in this department, ET: The Extra Terrestrial). In the 1980s, in the action parody They Live, the aliens were posing as Reaganite yuppies - clearly the greatest threat to American society then known to writer-director John Carpenter. While in the 1990s, a movie such as Independence Day had seemed to come full circle from the paranoia of the past and celebrated instead a new modern imperialism where America led the entire planet on a great big July 4th shoot-em-up. One of the low points of that movie is US President Tom Whitmore (Bill Pullman) announcing that all the earth's nations would, from then on, celebrate Independence Day with America, whether they liked it or not. It seemed to be a telling point of mass delusion from an empire at the height of its powers. It could, in reality, only go downhill from there.

Naturally, after 9/11, the alien-invasion movie carried weight. Steven Spielberg, when he came to direct his 2005 version of War of the Worlds, spoke solemnly of how his film was interested in the survivors of terror on the ground, and how they come together in the face of the atrocities around them. "9/11 has created a social atmosphere", he said at the time. "One that has provided me with a raison d'etre for telling War of the Worlds today, as opposed to 20 years ago."

And with the US-led invasion of Iraq an ongoing reality, the subject of war became equally burdened with gravitas. The desert battles in Michael Bay's Transformers movies hinted at strange beings, alien insurgents, that emerged from the sands, created chaos and destruction and then disappeared again. While even Avatar delivered its formulaic action via conspicuous lectures about invasion, imperialism and occupation. And with a plethora of new titles on the way, including Battle: Los Angeles 2011 (aliens invade LA) and The Darkest Hour (aliens invade, well, Earth) it would seem that the alien-invasion movie is as vibrant and as metaphorical as ever.

And yet. There's a big "and yet". Gareth Edwards, writer-director of Monsters isn't so sure. When asked if his movie is a metaphorical statement about immigration and American isolationism, he baulks. "That's completely accidental!" he says. "Whatever country we set this in, we were going to have aliens and a giant wall. If we did it in Australia people would've said, 'Oh, it's about the Aborigines!' If we did it in England they would've said it was about Eastern Europeans! It's inevitable, but it was never on my agenda."

Similarly, Greg Strause, co-director (with brother Colin) of Skyline, says his film was motivated not by ideological impulses but by industrial decisions and technological advances. Strause, a former special-effects artist (he worked on Avatar) explains that the motivation behind Skyline, which was made for under $10 million (Dh36.7m), was simply to demonstrate that you didn't need hundreds of millions of dollars to create a special-effects movie that can hold its own against the blockbuster heavyweights from the studios. "We wanted to create a fun ride, and to show that the way the business operates is inherently inefficient, that money is wasted, and that special-effects movies don't have to be expensive. Which we did."

Indeed, Edwards goes further and argues that there's a whole generation of technically gifted filmmakers (including the Strause brothers and Moon's director Duncan Jones) emerging from the world of commercials who want to tell sci-fi stories efficiently, and who are motivated not by heavyweight metaphor and meaning but, like Edwards himself, by the creative freedom that cheap digital technology allows them. They are here to show us, he says, "that science-fiction films are not the sole preserve of the studio system." And they are here to make films where special effects are impeccable. Where creative freedom is unimpeded. And where big-screen aliens, just very occasionally, are just aliens.

Skyline is due to be released in the UAE next Thursday