Abstract: During the manufacture, installation, and operation processes of DC gas-insulated metal enclosed switchgear (GIS) and gas-insulated transmission line (GIL), the introduction of metal particles is inevitable, leading to a decline in equipment reliability. Investigating the motion characteristics of metal particles and proposing detection and suppression methods are of great significance for the reliable operation of GIS/GIL. Over the past five years, we and our research team have focused on fundamental research into the issue of metal particles within DC GIS/GIL and validated their findings on ±320 kV DC GIL and ±550 kV DC GIS systems. This paper reviews the research conducted by our team over the last five years and highlights key findings. First, the sources and motion characteristics of metal particles are summarized. Second, our team's work on suppression strategies for metal particles is outlined and the results from photon-counting-based detection methods are summarized. Finally, the urgent research directions and critical issues concerning metal particles in DC GIS/GIL systems are discussed.