/sci/ - Science & Math

5. Nearly all interactions between atoms in a molecule are down to the electromagnetic force, but it can manifest in several different forms of bonds such as hydrogen bonding, covalent and ionic bonds, dipole-diplole interactions and so forth.

In highly unusual cases, such as at very high pressures, the strong nuclear force can also have a tangible effect, resulting in fusion of individual atoms.

Gravity also provides slight bond, but this is so incredibly weak that everybody (aside from a few weird theoretical physicists) ignore it.