Wind turbine blades comprising one or more deformable trailing edge sections having a multistable sheet comprising a plurality of bistable elements, each bistable element having two stable positions, wherein the multistable sheet is attached in a cantilever manner to a structural portion of the blade and extends in a chordwise direction, and the multistable sheet is connected to a skin of the blade such that upon changing one or more bistable elements from one stable position to the other stable position a shape of the trailing edge section changes. The application further relates to wind turbines comprising such blades and methods of controlling loads on the blades.