Ionic bonds form between nonmetals and metals.
The reason ionic bonds are formed is because nonmetals and metals usually have high electronegativities, which essentially means that metals pull on nonmetals' electrons.
When a metal takes an electron from a nonmetal, the metal becomes negatively charged and the nonmetal becomes positively charged. Because opposite charges attract, the two atoms will stick together, thus forming an ionic bond
-T.B.
