Particles move in a plasma under the influence of fields. The latter can be externally imposed, i.e., in the form of so-called external electric and magnetic fields. In addition, there is also an interaction between the particles themselves due to so-called internal fields, e.g., Coulomb fields in the electrostatic approximation. We ignore the internal fields in this chapter. In this chapter, we consider the motion of particles in prescribed electromagnetic fields. The latter can be spatially inhomogeneous. Any temporal dependence, if present at all, is assumed to be weak when considering drift motion. The specific aspects of the (relativistic) motion of a particle in an electromagnetic wave are treated in a separate section. Special aspects of Fermi accelerationFermi acceleration are treated separately. The chapter concludes with the motion of a particle under the influence of stochastic forces, i.e., within the framework of the Langevin approach.