why do metals have high melting and boiling points but non-metals have lowmelting and boiling points?

Metallic bonding involves a "sea ofelectrons" delocalised in a vast array of molecular orbitals that extend over the metal atoms. There are strong forces of attraction between these delocalised electrons and the positive nuclei of the atoms, which are relatively difficult to overcome and thus explain the high melting and boiling points of metals.nonmetals have lowermelting pointsbecause theirintermolecular forcesare weak, meaning that themoleculesare not held together as tightly as the metal molecules are so it takes much less to change from a solid to a liquid or a liquid to a gas.