Here's why:

* Metallic bonds: Metals bond with other metals through a "sea of electrons" where electrons are delocalized and shared throughout the structure.

* Ionic bonds: Metals react with nonmetals to form ionic bonds. In ionic bonding, the metal atom loses electrons to become a positively charged cation, and the nonmetal atom gains electrons to become a negatively charged anion. These oppositely charged ions attract each other electrostatically.

Covalent bonds involve the sharing of electrons between two nonmetal atoms.

In summary: When a metal reacts with a nonmetal, an ionic bond is formed, not a covalent bond.