These are chemical forces that are vitally necessary in larger macro-structures, especially in biological systems. They are:

1. Hydrogen bonds, the attraction between a positive atom and a pair of electrons on a negative atom.
2. Charge-charge interactions, electrostatic attractions between oppositely charged particles; ionic bonds.
3. Van der Waals Forces, the weakest of the three, which requires molecules in a minimum proximity, but repels if they get too close. Also can be called a dipole-dipole interaction.

Non-covalent intermolecular forces create weak, but stable bonds that can be formed and broken on the fly. This makes them very useful for protein formation and folding, among other things. Non-covalent intermolecular forces are much easier to break than covalent bonds .