As a metal is heated to its melting point, the metallic bonds keeping the atoms in place weaken so that the atoms can move around, and the metallic bonds eventually break completely at the metal's boiling point.
æz ɐ mˈɛɾəl ɪz hˈiːɾᵻd tʊ ɪts mˈɛltɪŋ pˈɔɪnt, ðə mətˈælɪk bˈɑːndz kˈiːpɪŋ ðɪ ˈæɾəmz ɪn plˈeɪs wˈiːkən sˌoʊ ðætðɪ ˈæɾəmz kæn mˈuːv ɚɹˈaʊnd, ænd ðə mətˈælɪk bˈɑːndz ᵻvˈɛntʃuːəli bɹˈeɪk kəmplˈiːtli æt ðə mˈɛɾəlz bˈɔɪlɪŋ pˈɔɪnt.