What is strange about the metal sodium?

Answer 1

The metal sodium at solid state is so much reactive that it readily oxidises itself with atmospheric oxygen and burns to give sodium oxide.

Answer 2

Sodium is strange because it is a soft metal that is typically stored under oil due to its high reactivity with air and water. When exposed to water, sodium can react violently, producing hydrogen gas and heat. Sodium is also commonly found in compounds like table salt (sodium chloride).