  We prove a normal form for strong magnetic fields on a closed, oriented
surface and use it to derive two dynamical results for the associated flow.
First, we show the existence of KAM tori and trapping regions provided a
natural non-resonance condition holds. Second, we prove that the flow cannot be
Zoll unless (i) the Riemannian metric has constant curvature and the magnetic
function is constant, or (ii) the magnetic function vanishes and the metric is
Zoll. We complement the second result by exhibiting an exotic magnetic field on
a flat two-torus yielding a Zoll flow for arbitrarily small rescalings.
