Three years ago, R and F and I decided to watch science fiction movies every Friday night. We decided to watch an old one and a new one, back-to-back. We thought it was important for F's cultural enrichment that she become familiar with those classics, like "Forbidden Planet" and "Earth v. the Flying Saucers". I told her that in the old movies, and probably most of the new ones, there's always a babe. But also that there are important Themes to be learned from these stories. Here are a few, with examples:

Don't Wake It Up ("The Thing from Outer Space"; "Raiders of the Lost Ark"; "Space Seed", the Star Trek ep that set up "Wrath of Khan")
Run towards it! (sarcastically said) ("The Monolith Monsters")
Don't Fool with Mother Nature/There are Things Man was Not Meant to Know (very common theme; examples include "Them!" and "Mimic", which are virtually the same story; also "Jurassic Park", of course)
It's Right Behind You ("Alien", "Jurassic Park")
They're Not Your Friend ("V", Twilight Zone ep "To Serve Man")
Evil Capitalists ("Aliens", "Jaws" which is really classic SF as I hope to demonstrate later)(a sub-theme of this is Don't Trust the Government, "ET")
You're Gonna Need a Bigger [blank] (Boat - "Jaws"; gun - "Aliens", "Predator 2")
Why are Humans So Puerile ("The Day the Earth Stood Still"; any Star Trek ep with Vulcans in it)
If You Knew What I Know/I Tried to Tell You ("Invasion of the Body Snatchers", "They Live", "Close Encounters of the Third Kind")
It's Not Dead Yet ("Terminator", "Predator 2")

Think of some more?