Leaves appear green because they contain chlorophyll. Chlorophyll absorbs the other colors of light wavelengths, leaving only the green reflected, and therefore visible to the human eye.
In addition to being green, chlorophyll catches the sun's rays and uses photosynthesis to turn those rays into chemical energy. More precisely, it turns carbon dioxide and water into a mixture of carbohydrates and oxygen. Chlorophyll is described as a light-trapping molecule, or a light-trapping receptor as well as a chelate. As a chelate, chlorophyll has a central metal ion that is bonded to an organic molecule of hydrogen, nitrogen, oxygen or carbon.