External energy assisted machining involves the use of a heating, cooling, and mechanical vibration source to facilitate the material removal process. A drastic attention on the external energy assistance is resulted from the requirements for newly developed hard and brittle materials machining and many activities to understand the mechanisms, processes, and the systems have been performed on both micro and macro scale in recent years. This paper attempts to provide an overview in the general idea of these areas with laser and plasma, cryogenic, and vibration assistances. The progresses made up to date will be explained in detail and finally, the future research directions in this area will be discussed.