Back to the "and" and the "or" in chemistry

That the "and" is present in the different types of bonding between elements is self evident. To continue our phenomenological description of these types of bonding, we have already described how in ionic bonding,  an electron on the outer shell of an atom pull away from this shell (the "or" in action), travels to  the outer shell of an adjacent  atom and joins the community of electrons there (the "and").   The attractive forces of the differently charged atoms binds them together.
In metallic bonding (which results in pieces of metal), we again see the "or" when an electron leaves the outer shell of an atom. Electrons leave the outer shells of other atoms, resulting in a sea of electrons outside the atoms (the "and" again).  This sea causes the different atoms to cluster together (another case of the "and") and also prevents them from moving.
 In covalent bonding, we see a compromise between the "and" and the "or". The electron doesn't quite leave the outer shell of one atom or join that of another.  Rather, the outer shells of different atoms share varying numbers of electrons with each other.  These shared electrons act as the glue that holds the atoms together.
As we've said, these differing types of bonding work to the benefit of the "and".  However, they also promote diversity (the "or") by enabling a seemingly infinite variety of combinations to be formed.