Final answer:
Atoms lose or gain electrons to achieve a stable electron configuration, not just metals. Metals tend to lose electrons and become cations, but nonmetals gain electrons to become anions. Electrical conductivity and other properties also distinguish metals from nonmetals.
Step-by-step explanation:
The willingness of an atom to lose an electron is related to its tendency to form cations, a property that is indeed one of the characteristics of metals. However, while metals do tend to lose electrons due to their lower electronegativities, it is not the sole criterion that defines a metal.
Atoms, whether metal or nonmetal, lose or gain electrons to achieve a more stable electronic configuration, which usually involves having a filled valence shell of electrons, akin to the noble gases. Metals, which typically have one to three electrons in their valence shell, lose electrons to achieve this stability, becoming cations in the process. Nonmetals, on the other hand, often have four or more electrons in their outer shell and can achieve stability by gaining enough electrons to fill their valence shell, resulting in anions.
The distinction between metals and nonmetals also involves other properties such as electrical conductivity, where metals are generally good conductors due to their free-electron model, which depicts electrons moving freely within the metal lattice.