Elements are classified as metals, non-metals, metalloids and inert gases. Which among them form electrovalent bonds?

Bonds formed between metals and non-metals are electrovalent bonds.

Metals have 1, 2 or 3 electrons in their valence shell. They have a tendency to lose their valence electrons. So they combine with non-metals which have 5, 6 or 7 electrons in their valence shell and thus have a tendency to gain electron(s) and form electrovalent bonds.