This is the first thing that we see Stiles search for after he decides that maybe Scott’s sudden talent on the lacrosse pitch might actually be supernaturally induced in 1×01. It is understandable that he would search silver bullets because they are so entrenched in traditional pop-culture surrounding the werewolf. However despite this piece of research nothing in the actual show has indicated that silver is actually harmful to werewolves.

Silver Bullet – Definition
According to folklore, the silver bullet is supposed to be the only kind of bullet that is effective against the Werewolf and other monsters.

Silver Bullet Information
The silver bullet is the only bullet that will kill a werewolf. Silver bullets differ from lead bullets in many ways. Silver bullets have less mass than a lead bullet of…

Silver Bullets Against Werewolves
Werewolves are extremely vulnerable to the silver bullet. It is said that to shoot a werewolf with a silver bullet not only kills the werewolf, but causes great agony…

However, this may all be symbolic because the hunters which have been killing werewolves for a long time have the surname Argent which means silver in French. Meaning that the truth may have gotten obscured over the years, leading to the myth that silver bullets kill werewolves when it is just people with bullets and the name ‘Silver’ that kill them. Argent is the Paternal name so it can easily be a very very old traditional family name.