Dean: Alright, so what do we know about this thing?
Sam: Well, uh, it was fast and it freaked when I cut it with silver.Sam: A ghoul? A zombie, a shifter, or about a dozen other things.
Dean: Alright, so that narrows it down to...
Silver in Supernatural
Dozens of creatures are vulnerable to weapons made of silver.
Silver bullets are used to dispatch:
- Madison and Glen, the werewolves in 2.17 Heart, as well as a werewolf Sam and Dean hunted as teenagers.
- The shapeshifters in 1.06 Skin, 4.05 Monster Movie and 6.02 Two and a Half Men
- Skinwalkers in 6.08 All Dogs Go to Heaven. Lucky is shot, but survives.
- Professor Ludensky the werewolf in 8.04 Bitten.
- Joy Myers the werewolf in 9.12 Sharp Teeth.
Silver blades, even those with a thin layer of silver plate on the exterior, are effective against:
- Another shapeshifter that is killed with a silver letter opener in 2.12 Nightshifter.
- The wraith in 5.11 Sam, Interrupted.
- The djinn in 2.20 What Is and What Should Never Be, 6.01 Exile on Main St. and 8.20 Pac-Man Fever, if it has been dipped in lamb's blood.
- Against lamias once the weapon is blessed, though Sam and Dean are not able to secure a blessing in 6.04 Weekend at Bobby's.
- Werewolf Michael Wheeler by Brian Wilcox in 8.04 Bitten.
- Werewolves Sheriff Pat, Russ and Joba in 9.12 Sharp Teeth
- Alonso the pishtaco in 9.13 The Purge
- A shapeshifter by Sam in 9.16 Blade Runners
Silver stakes are also used to "kill" zombies in 2.04 Children Shouldn't Play with Dead Things and 4.07 It's the Great Pumpkin, Sam Winchester; in the former, silver bullets weakened the zombie but did not kill it.
Silver does not need to kill the monster to have an effect on it. Wraiths burn when silver touches their skin. the skinwalker Lucky in 6.08 All Dogs Go to Heaven is restrained by Sam and Dean using silver chains. When confronted with a new, unknown monster, Dean suggests that silver bullets are their best chance.
Silver is therefore a useful test for hunters that allows them to see if they are dealing with a human. When Dean returns from Hell Dean cuts himself with a silver blade to try and demonstrate his humanity as does Sam on his return from Lucifer's Cage. In 4.19 Jump the Shark, Dean replaces the diner cutlery with silver utensils to test whether Adam Milligan is human. He does not react to the silver, but is not human. He is in fact a ghoul, a being unaffected by silver, pretending to be Adam. The Alpha Shapeshifter also appears to be immune to silver, as are leviathans.
Silver in History and Lore
Silver is a white, elemental metal believed to have been mined as early as 4000 B.C. It has been used for jewelry, tableware, coins, and dentistry. Silver is also valued, both in ancient and modern times, for its antimicrobial properties. Silver coins were sometimes placed in water barrels to prevent fouling, and surgical instruments can have a silver coating.
Traditionally, silver is associated with water, the moon, and moon goddesses, such as Selene. Because werewolves are said to change on the moon cycle, this may explain the theory that silver is their weakness.
Silver is appears in several popular sayings, including “Every cloud has a silver lining.” A “silver bullet” is a perfect solution to a problem.