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.
Wikipedia, High-explosive anti-tank warhead, 2019
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.
World of Tanks, Anti-Tank Rounds, 2019
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.
How could an illiterate man who lived 1400 years ago have known about armor-piercing?