Copper

Copper is a material found in the Overworld. It spawns naturally in copper ore, which drops raw copper, which can then be smelted into copper ingots.
Items
Copper Ingot - an item created by smelting raw copper or killing drowned.
Raw Copper - an item dropped from mining copper ore.
Spyglass - an item crafted with copper ingots and amethyst shards that can be used to zoom in on distant objects.
Brush - a tool crafted with a stick, a copper ingot and a feather. It can be used to brush suspicious sand, suspicious gravel and can be used to brush armadillos for scute.[upcoming JE 1.20.5 & BE 1.20.80]
Blocks
Copper blocks oxidize over time, gaining a verdigris appearance over four stages. They can be prevented from oxidizing by being waxed with honeycombs.
Block of Raw Copper − a block used for compact raw copper storage.
Copper Ore - an ore that can be found underground.
Deepslate Copper Ore - the deepslate variant of copper ore.
Lightning Rod - a block used to divert lightning strikes.
Copper - an element in Minecraft Education and Bedrock Edition.
Experimental
This feature is not enabled in-game by default and requires enabling the "Update 1.21" experimental data pack in Java Edition or the "Update 1.21" setting in the "Experiments" section in Bedrock Edition.
Mentioned
Copper Golem - an unadded mob that lost the mob vote at Minecraft Live 2021.
- Copper Button - an unadded block that would have been added if the Copper Golem won the mob vote at Minecraft Live 2021.
Removed
Copper Horn - an item that could play different melodies depending on which goat horn it was crafted with.
April Fools
Copper Spleaves - a joke item in Java Edition 23w13a_or_b which broke upon contact with entities, found in Lunar Bases.
Copper Sink - a joke item in Java Edition 23w13a_or_b which could delete copper-based items