The deformation fields within grains in polycrystalline materials are generally highly heterogeneous and can be the precursors to the nucleation of micro-cracks or cavities. Such behavior is conditioned by microstructural features, such as grain structure, texture, morphology, size, etc. The understanding of such complex phenomena is crucial to enable structural integrity assessments of engineering components, since it constitutes the physical bases on which to describe the local mechanisms of deformation and failure to be incorporated into structural integrity codes. This work provides a brief overview of the different continuum mechanics approaches used to describe the deformation behavior of either single crystals or individual grains in polycrystalline metallic materials. The crucial role played by physics based local and non-local crystal plasticity approaches in the prediction of heterogeneous deformation is discussed. Representative examples are given regarding the use of dislocation mechanics-based crystal plasticity frameworks to describe localized plastic deformation behavior of FCC polycrystalline metallic materials.