What is a defining characteristic of metals in relation to electrons?

A defining characteristic of metals in relation to electrons is their tendency to donate electrons freely. This behavior is rooted in the atomic structure of metals, which typically have one to three electrons in their outermost shell. Because these electrons are loosely held, metals can easily lose them, leading to the formation of positive ions. This property is fundamental to the metallic bond and influences their conductivity, malleability, and reactivity.

Other options present characteristics that are more associated with non-metals or specific chemical behaviors not typical of metals. For instance, accepting electrons to become stable is more characteristic of non-metals. Forming covalent bonds exclusively is not accurate since metals predominantly form metallic bonds and ionic bonds rather than covalent bonds, which are more common among non-metals. Finally, metals do not have a complete outer electron shell; rather, they seek to lose their outer electrons to achieve stability, contrary to the notion of having a complete outer shell, which is typically found in noble gases.