Here's why:

* Cations are positively charged ions. This is true, regardless of whether they are formed from metals or nonmetals.

* Cations are formed when an atom loses electrons. This loss of negatively charged electrons results in a net positive charge.

* Metals tend to form cations. This is because they have a relatively low ionization energy, meaning it's easier for them to lose electrons.

* Nonmetals tend to form anions. Nonmetals have a higher electronegativity, making them more likely to gain electrons and become negatively charged.

Examples:

* Sodium (Na) is a metal that forms the cation Na+ by losing one electron.

* Chlorine (Cl) is a nonmetal that forms the anion Cl- by gaining one electron.

However, there are exceptions:

* Hydrogen (H) is a nonmetal that can form both the cation H+ and the anion H- depending on the chemical environment.

* Some nonmetals can form cations under specific conditions. For example, ammonium (NH4+) is a cation formed by the combination of nitrogen and hydrogen.

Therefore, it's inaccurate to say that cations are always nonmetals. Cations can be formed from both metals and nonmetals.