Given that axions are both a promising candidate to solve problems in the Standard Model and are ubiquitous in quantum gravity, it is crucial to accurately determine their signatures. In this talk, we discuss how the axion's compact field space leads to interesting interactions with topological defects, specifically monopoles and strings. In the case of monopoles, we show that, due to the Witten effect, axions interacting with abelian gauge fields generate a potential for the axion from loops of magnetic monopoles, and discuss a simple phenomenological example where this potential is the dominant contribution to the axion mass. In the case of strings, we discuss superconductivity from massless chiral excitations along the string. We show that bulk fermions do not need to become massless in the core of the string for there to be trapped massless excitations, and explore the counterintuitive phase structure of these zero modes, which become less localized to the string as the mass is increased.