Brush for applying mascara and container

A brush for applying a makeup product, in particular for applying mascara to the eyelashes or a dye to the hair, including a plurality of bristles held between the spirals of at least two branches of a helically twisted metal wire that forms the core defining the longitudinal axis of the brush, wherein over at least a portion of a brush, some of said bristles are provided at the surface thereof with at least one groove extending substantially from the base to the tip of said respective bristles, and some of said plurality of bristles having cross sections which have different shapes from that of other of said bristles, so that said plurality of bristles comprise at least two types, and that the bristles, having different cross-sectional shapes, are spaced apart along said axis of the core, and that a space exists between the bristles to permit the penetration of the eyelashes or hair, the bristles of different cross-sectional shapes resulting in filling of different amounts of the product along the brush, some of said bristles having a cross section area larger than other of said bristles and the bristles having a cross section of larger area being made of a material capable of softening when it is dipped into the product intended to be spread by the brush.