Why does a chimmey have lead flashing?

A chimney has lead flashing to create a watertight seal where the chimney meets the roof. Lead is a durable and malleable material that can conform to irregular surfaces, preventing water from leaking into the roof structure. This helps to protect the roof and the interior of the home from water damage and potential mold growth. Additionally, lead flashing is resistant to corrosion, ensuring long-lasting protection.