All atoms and molecules show London Dispersion Force, a primary way atoms and molecules interact. Most of the time, molecules have additional stronger forces than the London Dispersion Force, which is the weakest. Therefore, London Dispersion forces are exclusively seen in the nonpolar molecules since they don't have other competing functional groups leading to other interfering intermolecular interactions.
The nonpolar molecules have a low electronegativity difference of less than 0.5 between the two atoms in a covalent bond. There is no charge separation or poles in such nonpolar molecules. A few examples are H2, N2, CH4, CO2, and He.
The above excerpt supports the chapter Intermolecular Forces part of CurlyArrows' Introductory Organic Chemistry Course. Preview the Book.
Related Reading: Introduction to the Vander Waal Forces, London dispersion force
