Elements that make up the compounds that are characterized as covalent are mostly in the right part of the periodic table.
Alkalyne metals and alkalyne earth metals, which are located in the left part of the table, and given that those elements form ions with relative ease they make up ioinic compounds.
Covalent compounds are made up mainly of a non metal element and a metal elements with low metallic properties.
The metallic character of the elements decrease as you go to the right of the periodic table, that is why you found those elements in the right part of the periodic talbe.