A brush includes a substrate, a number of brush bristles, a storage bag, and a pushing element. The substrate includes a main body and a handle extending from the main body. The main body has a first loading surface supporting the brush bristles. The first loading surface defines a through hole. The main body defines a first receiving groove communicating with the though hole. The handle has a second loading surface, and defines a second receiving groove communicating with the first receiving groove. The second receiving groove passes through a portion of the second loading surface adjacent to the first receiving groove. The storage bag receives paste, and is received in the second receiving groove and partially extends into the first receiving groove to communicate with the through hole. The pushing element squeezes the storage bag to make the paste flow into gaps between the brush bristles.