Copper is commonly used in armor-piercing.
A high-explosive anti-tank (HEAT) warhead is a type of shaped charge explosive that uses the Munroe effect to penetrate thick tank armor. The warhead functions by having the explosive charge collapse a metal liner inside the warhead into a high-velocity superplastic jet. This superplastic jet is capable of penetrating armor steel to a depth of seven or more times the diameter of the charge but is usually used to immobilize or destroy tanks.
Contrary to popular belief, HEAT rarely reaches above 600°C and is incapable of melting treated steels, which can easily withstand temperatures of 1400°C. It is the sheer pressure from the explosion that pushes through the armour, projecting inside the tank a blast of copper fragments from the liner that was holding the charge together.
The explosion pushes and reshapes the copper liner and this is what actually penetrates into the armor. However this armor-piercing technique was portrayed in the Quran 1400 years before it was discovered.
Quran [55.35] You will be bombarded with projectiles of fire and copper, and you shall not be victorious.
Projectiles of fire and copper turned out to be an armor-piercing technique.