Chemical bonding is defined as the attraction between elements, ions or molecules which results in the formation of compounds. The bonding takes place due to sharing of electrons as in covalent bond or by the electrostatic force of attraction between positive charge ion (cation) and negative charge ion (anion) as in ionic bond.
Now, electrons are the negative charged particles of an atom and it is found in clouds which is surrounded by the nucleus of an atom. Electrons play a vital role in chemical bonding. In both type of bonding i.e. ionic bonding in which electrons are transferred from on atom to other atom and covalent bonding which results due to sharing of electrons between two atoms.
Thus, electron is a part of an atom is most directly involved in chemical bonding.