The invention relates to a method for forming powder particles, wherein the method comprises feeding a start material mixture including more than one constituents in the form of granules into a reactor comprising a reaction zone and a heat source, performing thermal synthesis in the reaction zone in which the start material mixture is moved and the constituents of the start material mixture react in the presence of heat so that the reaction is started by means of heat of the reactor and energy of the start material mixture is released in the form of heat in order to achieve the reaction, and producing powder particles during the reaction. Further, the invention relates to a powder particle product.