The deployment of hydrogen in energy systems represents a pathway to achieve the net-zero emissions and climate neutrality goal. Metallic components used in hydrogen-containing atmospheres can experience severe degradation in mechanical properties due to hydrogen-induced damage. Metal additive manufacturing, particularly laser powder bed fusion, has been recently deployed to produce various metallic components  used in energy systems, and it becomes more important to understand the mechanical behavior of their alloys under the influence of gaseous hydrogen. This should enable both of the process optimization of additive manufacturing and the materials development for hydrogen-based energy systems. In this study, various metallic alloys (e.g. 316L, Ti6Al4V, and Fe-Cr) were manufactured by the laser powder bed fusion additive manufacturing process. Various samples for metallographic investigations as well as for mechanical testing in different modes (tensile and fatigue) were prepared by applying different process-parameters sets and in different conditions (as-built and heat treated). For testing under gaseous hydrogen, hollow specimens were manufactured and filled with hydrogen gas up to 20 bar and tested in low cycle fatigue mode to determine the degradation in fatigue lifetime induced by exposure to hydrogen. The microstructures were carefully characterized on different length scales to explore the influence of hydrogen on the mechanical properties and the corresponding deformation mechanisms. The effect of process-induced heterogeneities (e.g. grain sub-structures, dislocation networks, and elemental segregation), on the mechanical properties, damage and deformation mechanisms and fracture characteristics induced by testing under hydrogen will be discussed. The findings offer insights into the influence of additive manufacturing-related microstructure features on the mechanical behavior under hydrogen, and the study highlights the opportunity to utilize the microstructure heterogeneities in tuning the hydrogen-resistance of additively manufactured metallic alloys.