Rule of thumb answer is covalent bonds form between non metal elements.
Covalent bonds usually form between two nonmetals/
The question is probably more "Which elements form covalent bonds?" Ionic bonds are between a metal and a non-metal. COVALENT bonds are between two non-metals.
Aluminium will form covalent bonds with other elements if the difference in the electronegativities between the two elements are below 1.7
Covalent bonds form betweenthe electrons in the outer valence of an atom.Read more: What_do_covalent_bonds_usually_form_between
Why does group 4A elements tend to form covalent bonds rather than ionic bonds? 
Covalent bonds are between nonmetals.
Covalent bonds usually form between two nonmetals/
The question is probably more "Which elements form covalent bonds?" Ionic bonds are between a metal and a non-metal. COVALENT bonds are between two non-metals.
Elements form bonds because of the attractions between atoms or ions. There are several types of bonds such as ionic, covalent and metallic bonds.
Aluminium will form covalent bonds with other elements if the difference in the electronegativities between the two elements are below 1.7
Why does group 4A elements tend to form covalent bonds rather than ionic bonds? 
Covalent bonds form betweenthe electrons in the outer valence of an atom.Read more: What_do_covalent_bonds_usually_form_between
covalent bonds
There are two kinds of bonding; ionic and covalent. Ionic bonds form between metals and non-metals. Covalent bonds form between non-metals
A non-metal and a non-metal form covalent bonds.
The elements carbon and hydrogen both form primarily covalent bonds.
Bonds between non metal elements are usually covalent.