A monomer is a molecule that can bind with identical molecules to form polymers through chemical bonds or polymerization. The most common natural monomer is glucose, which forms polymers like cellulose and starch that make up over 77% of plant matter. Polymers consist of repeating units of monomers joined by covalent bonds to create large macromolecules. Polymer chains are made up of many monomers joined together, and their characteristics determine the polymer's properties and interactions. There are several types of polymer chains including linear, branched, and cross-linked polymers.