Before Science Fiction became successful (Planet of the Apes) and respectable (2001: A Space Odyssey) in 1968, Hollywood treated it like a secondary genre. Classics were still created (Day the Earth Stood Still, The Thing From Another World, Invasion of the Body Snatchers), but usually on small budgets. Forbidden Planet (1956) was one exception in which Hollywood took a chance on a lavish production. Unfortunately, the film did poorly at the box office, thereby confirming Hollywood's bias against SF for another decade.

One of the reasons Forbidden Planet may have done poorly financially is that its hardcore SF; it's more concerned with ideas and extrapolation than it is with action and emotional drama. But for fans of the genre, its attempts at verisimilitude, at making science and technology as plausible as possible, are its greatest strengths. (This is illustrated even by its throw-away moments: the area has to be secured before the ship's commander is allowed to disembark. This kind of protocol was missed by Star Trek: The Original Series and had to be corrected for The Next Generation.) Like hardcore SF novels that deal with big ideas,Planet successfully creates what Damon Knight called a "sense of wonder". That's not to say the film neglects the motivations of its characters. In fact, psychology plays an important role in the film.

Obligatory Plot Summary
The United Planets Cruiser C57D lands on Altair IV to establish contact with an earlier expedition. It turns out that there's only one survivor of the original crew, Dr. Morbius (Walter Pidgeon), and his daughter Altaira (Anne Francis). Morbius has spent the last twenty years studying the technology of a now-extinct species called the Krell. He warns Commander Adams (Leslie Nielsen) to stay away, for a mysterious and destructive force exists on the planet.

Analysis
Stephen King once explained why The Thing From Another World had an anti-intellectual/pro-military subtext. That attitude has also been attributed to Forbidden Planet. But I think Planet is saying the exact opposite.

The commander of Cruiser C57D is referred to as "Skipper", men who do a poor job while on watch are reprimanded, and the ship is equipped with weaponry so large that it has to be unloaded and assembled. It's clear that, for all its scientific trappings, C57D is a military vessel. And its commander is ostensibly the hero of the film. But the movie doesn't actually champion the military. The three officers who visit Morbius's house, Adams, Lt. 'Doc' Ostrow (Warren Stevens), and Lt. Farman (Jack Kelly) are quick to reach for their phasers on a number of occasions, forcing Morbius to reassure them that there's nothing to worry about. The military is shown to be too quick to react aggressively. It is also shown to be ineffectual. With the exception of one action taken by Doc, Adams and his crew can do nothing to stop the invisible creature that begins killing them off.