What is a bond between a metal and a nonmetal?
An ionic bond.
Ionic bonding involves the transfer of electrons from a metal atom to a non-metal atom until the outer shells of their resultant atoms are similar to that of a noble gas.
The metals lose electrons and form cations while the non-metals accept the electrons and form anions.
These oppositely charged ions are electrostatically attracted to each other and thus form extremely strong ionic bonds.