This is the latest entry in my series "Why Are They Scary?"
Of course, Werewolves frighten on a purely animal level wherein you try to keep yourself from getting ripped apart by fangs and claws as much as possible. On an entirely different level, the werewolf is a handy psychological shorthand for the beast inside us all. Like the Incredible Hulk, we each have a raging hellbeast trapped inside us that occasionally comes out in the form of snide comments, passive aggression or "accidental" traffic violations. For the worst of us, it comes out in domestic abuse, breaking things and other violence.
Michael Chabon has a short story collection called "Werewolves in Their Youth" and it is mainly about using werewolves as metaphors for the evil inside us all. It is a pretty great collection (including the story "Son of the Wolfman" in which a rape victim decides to keep her baby) and I would recommend it. For all the hue and cry over evolution not being real, our ancestors (superstitious as they were) could see the animal side in our actions and conclude that we had grown in time to quell those base impulses.
Either way you slice it, as an external monster lurking in the bushes to rip you apart or as an internal struggle to control your base urges, the werewolf is a formidable monster and my personal favorite.
For good portrayals of werewolves, check out the TV show Werewolf and the movie Dog Soldiers (to be reviewed at some point this year).