The movie, of course, features giant monster ants. This is scientifically implausible for a number of reasons, but so what. The ants also look really hokey, but the special effects available to directors back then were too limited for them to have done any better. What makes this movie stand out is that the writers clearly knew a thing or two about how to structure a horror story for psychological impact, and so did the director.
It's also interesting to see how familiar some of the underground scenes look to a modern movie-goer. From the scene where the soldiers use flamethrowers to destroy the eggs, to the hunt for the missing queen, to the battles in claustrophobic tunnel settings, this movie obviously had a major influence on the “Alien” franchise.
If anyone ever chooses to remake “Them!” using modern special effects, it could be a truly scary and exciting movie. The original version is hampered by the unrealistic-looking ants, but the storytelling is superior. I have a feeling this is going to remain one of my favorite creature features.