In hot mechanical forming, large scale machines with varied tooling exert forces on rough feed stock under controlled temperature to produce objects of the desired shape. The plastic deformation and thermal softening are only possible through a system of internal atomistic mechanisms, both dynamic (during straining) and static (afterwards), which define the flow stresses and determine the final microstructure and properties. The objective of this paper is to explain the pertinent features of both macroscopic processing and microscopic mechanisms, in order to be able to predict both the forces and the product quality.