Metals react with oxygen in the air to form metal oxides through a chemical reaction known as oxidation.

In more detail, when a metal interacts with oxygen, a chemical reaction occurs where the metal atoms lose electrons to the oxygen atoms. This process is referred to as oxidation. As a result of this reaction, the metal atoms become positively charged ions, while the oxygen atoms become negatively charged ions. These ions subsequently combine to create a compound known as a metal oxide.

For instance, when iron is exposed to air, it reacts with oxygen to produce iron(III) oxide, commonly referred to as rust. The chemical equation for this reaction is given by:

Similarly, when magnesium is burned in air, it reacts vigorously with oxygen, producing a bright white light and forming magnesium oxide. The chemical equation for this reaction is:

The speed and intensity of these reactions can vary significantly depending on the type of metal and the specific conditions. For example, some metals, such as potassium and sodium, react so violently with oxygen that they ignite spontaneously. In contrast, noble metals like gold and platinum are so inert that they do not oxidize at all, even over extended periods.

The formation of metal oxides is a fundamental concept in chemistry, as it helps us understand the reactivity series of metals, which ranks metals based on their tendency to react with substances like oxygen. This concept also has practical implications in various fields, including corrosion prevention and the manufacturing of ceramics, glass, and other materials.