Laser Powder Bed Fusion (L-PBF) is a technique in which a layer of metal powder is deposited, melted and solidified using a laser to create a solid layer of metal, with consecutive 2D layers being micro welded to preceding layers to build up fully solid 3D components. This technique has been the focus of considerable interest from research groups and industrial sectors where it is acknowledged to be a multi-variate process capable of producing highly complex geometries in low volumes. One of the most important factors to control is the quality and properties of the powder feedstock used. In this chapter, the various properties of metal powders that have been shown to affect the quality of fabricated parts are discussed. How the powder flows and spreads within the L-PBF process, and how the shape, size and composition of powders are investigated and can lead to different defects and porosities in parts are presented. This chapter provides an overview of how the mechanical and thermal properties of powders can impact the L-PBF process. The sustainability and recycling of such material feedstock within the powder life cycle are discussed. The international standards for analysis and safety considerations of powder which are relevant to additive manufacturing are also presented.