Copper rods have a much wider range of applications than pure iron. Every year, 50% of copper is electrolytically refined into pure copper for use in the electrical industry. The copper referred to here must indeed be extremely pure, containing at least 99.95% copper. Even trace amounts of impurities, especially phosphorus, arsenic, and aluminum, can significantly reduce copper's conductivity.

The presence of oxygen in copper (small amounts are easily introduced during copper smelting) greatly affects conductivity; copper used in the electrical industry must generally be oxygen-free. Furthermore, impurities such as lead, antimony, and bismuth can prevent copper crystals from bonding together, causing hot brittleness and affecting the processing of pure copper. This high-purity copper is generally refined using electrolysis.

Red copper is a relatively pure type of copper, generally considered to be close to pure copper. It has good electrical conductivity and ductility, but its strength and hardness are somewhat inferior.