In episode 1 of The Mandalorian, the protagonist is given a chunk of metal that he then takes to another Mandolorian who melts it down and makes a shoulder piece for him.
What is this metal, and why does it seem so special to the Mandolorians?
This metal is used to make Mandalorian armor and can withstand blaster fire.
This Esquire article explains its importance for Mandalorians (emphasis mine).
This substance is described as "an alloy used in Mandalorian armor, notable for its high tolerance to extreme forms of damage. The metal was durable enough to withstand a direct blaster shot, and could potentially withstand the slash or glancing blow of a lightsaber, though could be penetrated with a direct stab."
This armor is worn by the warrior race from the planet Mandalore.