The nature of the cosmological dark matter and dark energy is still a mystery, although current and upcoming 21-cm measurements during cosmic dawn can provide a new arena on the search for these two fluids. This era saw the formation of the first stars, which coupled the spin temperature of hydrogen to its kinetic temperature---producing 21-cm absorption from the CMB. I will show how we can indirectly map the small-scale matter power spectrum through this 21-cm signal, as its timing depends strongly on the abundance of the small minihalos that hosted the first stars. This can tightly constrain dark-matter models with suppressed power, such as warm or fuzzy dark matter. In addition, I will describe how the acoustic physics of recombination are imprinted onto the 21-cm power spectrum during cosmic dawn, resulting in large velocity-induced acoustic oscillations (VAOs). These act as a new standard ruler at z~20, opening up searches for early dark energy and perhaps resolving the H_0 tension.