Some molecules can be linked together by covalent bonds into long chains to form very large molecules called macromolecules.If these molecules are made of the same repeating unit, the repeating unit is called a monomer and the long chain is called a polymer.Triglycerides (lipids) are macromolecules but not polymers. They are made of a molecule of glycerol linked to three long chain carboxylic acids (fatty acids).Starch is a polymer made of several hundreds to thousands of alpha-glucose molecules(monomers) linked together by covalent bonds.