We introduce the theoretical models for classical spins used in this thesis. First, we introduce a phenomenological model based on the Ginzburg-Landau theory for describing the thermodynamic properties of chiral magnets. Next, we introduce a minimal spin model, which describes the fundamental magnetic properties of chiral magnets both in and out of equilibrium. Then, we present a spin-charge coupled model for a metallic magnet in which the effects from itinerant electrons are explicitly taken into account. Finally, we introduce the effective spin model derived by the perturbation expansion for the spin-charge coupled model.