Lead

Lead was a metallic element.

Vardans could not broadcast themselves through lead. The Fourth Doctor had his Presidential chamber decorated with lead lining to keep the Vardans from reading his mind. (DW: The Invasion of Time)

Torchwood Three kept a radiation sponge in a lead-lined case. (TWN: Another Life)

On Venus, the Daleks forced Jeff Stone to work at a lead mine. (DAN: Red for Danger)

On Wengrol, Yend scientists built massive lead buildings to protect themselves from Mortain's radiation while they worked to find a cure for the mutations plaguing their world. (DWAN: The Sons of the Crab)

A lead-line coffin was used at the Eleventh Doctor's faked funeral at UNIT's Mount Snowdon base. Sarah Jane Smith and Jo Jones were able to survive the detonation of the base by hiding inside. (SJA: Death of the Doctor)