An ionic bond is a form of chemical bond where one metal atom loses the electron(s) to another non-metal atom to give it a full electron shell.

The metal that loses the electron(s) becomes a positively charged ion and the non-metal atom that gains the electron(s) becomes a negatively charged ion.

The two oppositely charged ions are attracted to each other with strong intermolecular forces creating an ionic compound, therefore they have a high melting point.

For example, sodium would lose one electron to chlorine which turns the sodium atom into a positive sodium ion and the chlorine atom into a negative chlorine ion.