A bullet was a projectile propelled by a firearm. Most bullets were made from a type of metal.

In human mythology, bullets made of silver could be used to kill a werewolf. A "real" werewolf like the Lupine Wavelength Haemovariform was unharmed by ordinary bullets; as the Tenth Doctor said to Captain Reynolds, "Bullets can't stop it." (TV: Tooth and Claw) Silver bullets were also utilised by the Brigadier to defeat the Destroyer. UNIT also used teflon anti-Dalek bullets and gold-tipped bullets for use against Cybermen. (TV: Battlefield)

In the Sontaran invasion of Earth in 2009, the Sontarans used a cordolaine signal excited the copper atoms in bullets and caused their expansion within a gun barrel, rendering Earth-made guns useless. The Doctor admonished General Staal for this, stating that "a Sontaran should face bullets with dignity". UNIT managed a counter-measure by using rad-steel coated bullets. This made the cordolaine signal ineffective. (TV: The Sontaran Stratagem/The Poison Sky)

Bastic bullets were used to destroy pre-war Daleks, (TV: Revelation of the Daleks) but eventually Dalek force field technology advanced to the point where bastic bullets were no longer effective against them. (TV: The Parting of the Ways)

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