Patina refers to the surface appearance that develops naturally or is artificially induced on metals over time. This finish is the result of oxidation, exposure to chemicals, or environmental factors such as moisture and air. Over time, metals such as copper, bronze, and brass will develop a distinct, colored surface layer known as a patina. The most famous example is the greenish-blue patina seen on copper structures, such as the Statue of Liberty.

In metal finishing, patina can also be created artificially through chemical treatments, allowing metal surfaces to acquire the desired color and texture. This technique has become a popular choice for designers, architects, and artisans looking to add character and personality to metal objects or building facades