A metal mask, a display panel and a display device are proposed. The metal mask comprises an opening region and a peripheral region surrounding the opening region. The peripheral region is provided with a first groove, the first groove may surround the opening region. By arranging a first groove surrounding the opening region in the peripheral region, sagging of the metal mask during the fabrication of the display panel can be decreased effectively, and tension of the metal mask can be reduced, which improves the thickness uniformity of an inorganic encapsulation layer formed by using the metal mask, thereby achieving a higher production yield of the display panel.