Oils have lower melting points than fats, and are liquid at room temperature. Plants produce oils. Both fats and oils serve important rols in the storage of chemical energy. A similar lipid group, the phospholipids, is built of glycerol, two fatty acids, a phosphate, and a nitrogen-containing group. They play key roles in the structure of cell membranes.
Waxes are important as waterproofing agents.
Steroids are complex molecules based on a sterol group. The steroids include testosterone, estrogen, and progesterone.