A precious metal, such as platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), silver (Ag) and gold (Au) are metals that are particularly chemically stable and do not react with their environment under normal conditions. They are generally resistant to oxidation and corrosion, even in contact with most acids.

Noble metals often have a high affinity for adsorbing reactants on their surface, which facilitates reactions by stabilizing transition states and lowering activation energies, which is why they are often found in catalysis.

The best-known example is the 3-way catalyst in automobiles. Platinum, palladium and rhodium reduce harmful gases such as carbon monoxide (CO), unburned hydrocarbons (VOCs) and nitrogen oxides (NOx) to less harmful substances such as carbon dioxide, water and nitrogen. Apart from that, precious metal catalysts play a major role in industry. Some platinum-based catalysts are used for the total oxidation of pollutants, among other things, while palladium plays a major role in hydrogenation reactions such as the hydrogenation of oils.

Since precious metals have an economic value in addition to their chemical value, it is worthwhile to recover even the smallest amounts from products, which is why catalysts containing precious metals are usually recycled.