abstract: In this talk, I will review recent progress for half-wave maps equation (HWM) with target S2, i.e., the standard two-dimensional sphere. (HWM) is a Hamiltonian geometric evolution equation with energy-critical scaling behaviour. I will focus on soliton solutions, rational solutions, and the underlying Lax pair structure that was recently discovered. This is joint work with Patrick Gérard (Orsay) and Jérémy Sok (Basel).