* Metals tend to lose electrons: Metals have a relatively low electronegativity, meaning they don't hold onto their electrons very tightly. When they react with other elements, they often lose one or more electrons from their outer shell.

* Cations: The loss of electrons results in a net positive charge on the metal atom, which is now called a cation. The number of positive charges on a metal cation corresponds to the number of electrons it has lost.

Example:

* Sodium (Na) is a metal. It has one electron in its outer shell. When it reacts, it loses that electron to form a sodium ion (Na+) with a single positive charge.

Important Note: While most metal ions have a positive charge, there are some exceptions, like the mercury(I) ion (Hg₂²⁺) which is a diatomic cation with a positive charge.