The 21-cm cosmological signal is gradually becoming a reality, offering a new insight into previously under-explored epochs. As with other cosmological observations, it is intriguing to consider what 21-cm cosmology can teach us about new physics. To address this, I will provide a concise overview of the physics behind the 21-cm cosmological signal and the effects of various new physics models on it. The discussion will then focus on hidden sector models that contain particles that scatter off baryons elastically. Specifically, I will argue that the Hydrogen Epoch of Reionization Array (HERA), aimed at measuring the 21-cm power spectrum, is likely to either confirm or exclude the possibility that DM-baryon interactions are the source of the anomalous measurement reported by the EDGES collaboration in 2018.