When I made this film I remember some guy came up to me and said that at the end of the movie the werewolf is killed with bullets and you can't kill a werewolf with bullets. He went on and on about the fact that you can only kill a werewolf with silver bullets, which struck me as so funny. Because, it's like, 'Really? How many werewolves do you know?'In fact, most of what we know about monsters was made up for movies and fiction. Werewolves in myths were never unfortunate creatures who were victims of a curse. They were witches who changed shape with the help of a skin made from wolf or human skin. They changed into an actual wolf in order to inflict evil on their neighbors - things like killing livestock. When caught, their skin was seized and they were burned at the stake.
"Silver bullets specifically come from Curt Siodmak, who was the original screenwriter of The Wolf Man. In one of the sequels he talks about silver bullets being the way of killing werewolves. He talked about where that came from once with me and he said he happened to be listening to The Lone Ranger on the radio and he thought, 'Silver bullets, that's great!' So he made that up. So much of what we accept as folklore and mythology is invented by screenwriters.
Bram Stoker made a serious effort at staying true to folklore but there are dozens of vampire myths and they are not consistent. Sometimes the only reason for driving a stake through a Vampire's heart was to pin him in his grave. A vampire had to be back in his grave by dawn and there were ways of keeping him out too late. If you spilled seeds or left a tangled string, he would be distracted tidying things up until dawn. One variety would strip his shroud off when he rose and put it back on when he went back to his grave. If you could find the shroud and hide it he would keep looking for it until it was too late.
Most vampires couldn't turn into other creatures but sometimes their heads were on backwards or they would have books for feet.
Stoker's version of the vampire and the stripped down Hollywood version was the accepted version for decades. It didn't really change until Anne Rice's Interview With the Vampire showed that a writer could change the rules. Since then, every writer decides how vampires work. The only constants are their aversion to sunlight and thirst for blood. Now some vampires just sparkle in sunlight instead of dissolving.
Werewolves' makeover came later and the Hollywood idea of werewolves being cursed was never lost. Starting in the 1980s, writers started taking advantage of research on real wolves and making their werewolves act more like the real thing. Before the 1980s werewolves were always solitary. Since the 1990s they are almost always in a pack.
While it is generally accepted that silver bullets hurt werewolves, vampires were not always susceptible. In Love at First Bite, Dracula is shot in the heart with three silver bullets by Dr. Rosenburg. Dracula's response, "No, Rosenberg, that is a werewolf ." As he is being hauled away (for shooting someone in public), Rosenburg says, "No harm done! The man's all right! This was for a werewolf! No problem! Calm down! Take it easy! I'm a doctor! I know where I'm going!" Since then most fiction has vampires affected by silver. It makes a convenient substitute for religious objects in these multicultural times.