Horror movies have changed dramatically over the decades to keep up with ever-evolving audiences. Some of the old classics, while still artful and entertaining, no longer have the power to shock. Others, however, have stood the test of time.
What makes a movie scary? Some would say it's the jump-scare _ the "boo!" moment that jolts you out of your seat. Others might point to a particularly ghastly monster or a preponderance of gore. And who's to say what's more terrifying _ a ghost, a creature or a plain old murderer? Much of what jangles your nerves depends on the fears you bring into the theater.
The best horror movies find a sweet spot: A primal, universal terror made vivid by skillful filmmaking. That formula will surely never age. Here, just in time for Halloween, are 20 of the scariest movies of all time:
