Why Alkali metal and alkaline earth metal form cation?

Answer 1

alkaline earth metals and alkali metals have 2 and 1 electrons in their outer most shell and are not tightly bound to nucleus so they are ready to lose their outer most electrons to form mono and divalent cations.

Answer 2

Alkali metals and alkaline earth metals have low ionization energies, making it easier for them to lose electrons and form cations with a positive charge. By losing electrons, they attain a stable electron configuration similar to that of noble gases, which enhances their stability.