Cables are aliens from another planet that use computers to reproduce. Below is a quick list of a few important things I learned from the film that I never knew before, and a few lessons that were inferred from the plot. I wish to thank the creators of ID4 for making these facts much clearer to me.
Aliens like to blow up significant land marks first.
All pro-UFO people are morons who dance atop the building directly under the Death Ray. The Law of Averages says you'll survive the Death Ray. The Law of Averages says you'll get waxed by the Death Ray. Strippers got moxie. When the going gets tough, they can drive California Highway Department utility vehicles, collect refugees and use their extensive survival skills to provide food and comfort to survivors.