Cannonball metal is a term used to describe IRON, which is a chemical element with the symbol Fe and atomic number 26. It is a metal that is malleable, ductile, and strong, and is the most common element on Earth by mass. IRON is used in many applications, including the production of steel, which is an alloy of IRON and other elements. Cannonball metal is often used to make cannonballs, which are solid projectiles that were historically used in warfare.