Copper is a metallic element and also a transition element, with the chemical symbol Cu and atomic number 29. Pure copper is a soft metal, with a reddish-orange metallic luster when the surface is just cut, and a purple-red color when the single substance is present. It has good ductility, high thermal and electrical conductivity, so it is the most commonly used material in cables and electrical and electronic components. It can also be used as a building material and can form many kinds of alloys. Copper alloys have excellent mechanical properties and very low resistivity, among which bronze and brass are the most important. In addition, copper is also a durable metal that can be recycled many times without damaging its mechanical properties.

Copper salts are the most common copper compounds. Their hydrated ions are often blue, while chlorine as a ligand is green. They are the source of the color of minerals such as azurite and turquoise, and have been widely used as pigments in history. Copper building structures will produce verdigris (basic copper carbonate) when corroded. Decorative art mainly uses metallic copper and copper-containing pigments.

Copper is one of the earliest metals used by humans. As early as prehistoric times, people began to mine open-pit copper mines and use the copper they obtained to make weapons, tools and other utensils. The use of copper had a profound impact on the progress of early human civilization. Copper is a metal that exists in the earth's crust and oceans. The content of copper in the earth's crust is about 0.01%, and in some copper deposits, the content of copper can reach 3% to 5%. Most of the copper in nature exists as compounds, namely copper ores.

The activity of copper is relatively weak, and the reaction of iron with copper sulfate can replace copper. Copper is insoluble in non-oxidizing acids.