It is clear from astronomical observations that there is a missing mass throughout the Universe. About \(90 \%\) of mass is missing and is called dark matter. There are dozens of possible dark matter candidates, but the only two that are seriously possible are Axions and Neutralinos. Between the two, neutralinos are theorized to be the most likely dark matter candidate because it is a cold dark matter particle and in order to produce a Universe like the one we observe, you need CDM to clump and form galaxies. Neither a neutralino or an axion has been detected and are thus still theoretical particles. In the future, when we have a larger, new generation of particle accelerators, physicists and astronomers will be able to prove if neutralinos exist. Until then, there are many other experiments being conducted to find these mysterious particles, but no experiment has been conclusive. Only the future will tell what dark matter is and what it is composed of, that is as long as MOND (a modification of Newton’s law of gravity) is incorrect.