Despite the successes of the Standard Model of particle physics, there are still key outstanding questions that render our understanding of the universe incomplete. In particular, a full picture of the universe requires physics beyond the standard model (BSM) in the dark sector, the gravitational sector, and early universe. In this talk, I will summarize these gaps in the current paradigm of particle physics and discuss how cosmology can be used as a powerful probe of new physics alongside terrestrial experiments. I will highlight several well-motivated particle candidates, including dark photons, Kalb-Ramond-like particles, higher spin particles, and axions as examples of BSM physics which aim to fill in these gaps. Finally, I will conclude with a discussion of future directions and prospects for addressing these open questions.