Having a copper weapon wielded while suffering shock damage has a lightning rod effect: it causes you to take extra damage, but completely protects all your rings and wands from being destroyed.

The Staff of Aesculapius should be made out of copper, since that is the antibacterial effective-against-disease material.

Copper items should generally be colored orange, not yellow, since copper is closer to orange than yellow. (Possibly an exception for explicitly brass items such as the brass lantern, but that might get confusing.)

Copper weapons get a bonus versus Kops.

It’s harder to force the lock on chests or large boxes made of metal, and increases the chance your weapon breaks. Additionally, the material of the weapon used to force the lock affects the result, if it’s used to pry rather than bash:

• Iron and metal behave as normal.
• Mithril is stronger than iron, and breaks less.
• Copper is slightly weaker than iron, and breaks a little more often.
• Softer metals, such as silver and gold, break less often but tend to bend. A “bent” weapon doesn’t actually become bent internally; it just loses a lot of enchantment.
• Wood is about as good as copper.
• Glass almost always breaks, and can break even if used to bash open a lock.

Hitting monsters that have a passive shock attack with something made of copper, silver, or gold increases the amount of shock damage.

Wielding a copper object or wearing copper armor protects against an otherwise successful disease attack some of the time, because copper is antibacterial.

Non-erodeproof copper items corrode over time.

Iron and copper items engulfed by gelatinous cubes get corroded in the process.