Cosmic rays comprise a significant amount of energy in galaxy clusters, and are as energetically important in galaxies as the thermal gas. A careful treatment of cosmic ray transport is necessary to predict dynamics (such as CR driven winds) based on the radio observations which indicate their abundance. Yet the physics of cosmic ray transport are not very well understood. In this dissertation I will discuss how cosmic rays travel through and couple energetically with magnetized plasma, focusing specifically on the effects of streaming and heating in cluster and galactic environments.