What do the metals calcium, magnesium, sodium, potassium, copper, and iron have in common?

Every one of these elements can react with oxygen to form
an oxide or if oxygen and water are present, a hydroxide. For example, iron and oxygen
chemically combine to form rust, or iron oxide. Sodium will burn in oxygen to form
sodium peroxide. Because all metals to an extent will react with oxygen, most are not
found in a pure state in nature, rather, they are found in a compound usuallly as an
oxide. When a copper structure like a statue, or when found as an architectural element
on a building is seen, it is usually green due to the fact that you are looking at
copper oxide. Therefore, the answer is that all of the elements react with
oxygen.