This Special Issue features research and review articles on the characterization of metallic materials during various processes such as solidification, forming, and heat treatment. This issue focuses on all characterization methods, including all forms of microscopy (transmission electron microscope, scanning electron microscope, etc.) and analytical techniques applied to the materials' microstructure, interface, surface, etc. Studies focusing on analysis using computational science are also welcome. Recent studies dealing with the behavior of materials during various phenomena (solidification, phase transformation, oxidation, diffusion, deformation, and so on) that can occur in processes such as casting, plastic working, and heat treatment are suitable for publication in this issue. This Special Issue will provide material scientists with up-to-date information explaining the behavior of many types of metallic materials using novel approaches. This issue covers all kinds of metallic materials.