The mechanical property and corrosion resistance of metals are often degraded by hydrogen absorption during metal production and environmental exposure. The material degradation induced by hydrogen greatly endangers the performance and safety of metals for applications in mechanical manufacturing, infrastructures and energy industries. Hydrogen embrittlement and hydrogen damage are two major types of hydrogen effects. The material design and protection to improve antihydrogen performance shall be based on the knowledge of how hydrogen interacts with typical microstructural defects in materials. In recent years, the investigation into microscopic mechanisms in hydrogen embrittlement/damage has been sped up by the instrumental advancement in insitu transmission electron microscopy, quantitative nanomechanical testing, atom probe tomography etc. In this review, we will introduce the mechanistic progress of research in hydrogen embrittlement/damage, and highlight the hydrogen impact on the behavior of basic microstructural defects such as vacancy, dislocation, interface etc.