There are three main types of chemical bonding; covalent, metallic, and ionic.

Covalent bonding, either polar or nonpolar, involves the sharing of a pair of valence electrons by two atoms. The electron pair interacts with the nuclei of both of the atoms, holding them together. A covalent bond is similar in strenght or stronger than the ionic bond and much stronger than the hydrogen bond if it is between polar molecules.

Metallic bonding is when mobile valence electrons are shared among atoms in a usually stable crystalling structure. A more stable configuration is usually achieved. It gets its name because metals usually have the characteristic of valence electrons being not tightly bound with the nucleus. This type of bonding allows each atom in a metal crystal to contribute all of the electrons in its valence shell to all of the other atoms in the crystal.

Ionic bonding is chemical bond that is achieved by the complete transfer of electrons from one atom to another. Typically it involves a metal and a nonmetal ion and the bond is formed by the attraction between the two oppositely charged ions. Sodium Chloride is a common example of an ionic bond. When sodium and chlorine are combined, sodium atoms lose an electron and chlorine atoms gain an electron.