The three types of bonding in chemistry are covalent, ionic, and metallic. Covalent bonds are strong and result in either giant covalent macromolecules, which are hard, strong and have high melting and boiling points, or simple covalent molecules, which have low melting and boiling points. Ionic bonds are also strong and result in hard, brittle ionic lattices that can conduct electricity when molten or aqueous. Metal bonds are weaker and result in malleable, ductile metal lattices that conduct electricity in all states.