The embodiment of the invention discloses a metal spring for a flexible cover, and relates to the field of structural design of flexible covers. The dual characteristics required by the flexible cover can be met while cost control is guaranteed. The metal spring for the flexible cover is composed of curved sections and straight sections at intervals in the two-dimensional plane, each straight section is arranged between the corresponding two adjacent curved sections, and the curved sections are elliptic arcs. In a fiber reinforced body formed by the metal springs, the metal springs are arranged in a grid mode, horizontal and vertical fibers of grids intersect at the straight sections of the metal springs. The metal spring is made of a high-elasticity steel material. The metal spring is suitable for the flexible cover of a self-adaptive bump air duct.