Solar flares, especially the strong ones, emanate from active regions including sunspots, where high magnetic non-potentiality resides in a wide variety of forms. Here we introduce several topics related to the flare-productive sunspots: (1) the statistical survey on flare-productive spots [Toriumi et al. 2017]; (2) the 3D MHD simulations of such flaring spots [Toriumi & Takasao 2017]; and (3) the flare loop modeling and reproduction of SXR light curves [Reep & Toriumi 2017]. Through discussing these topics, we broaden our scope to the possible applications of our knowledge of the Sun to corresponding stellar activities.