Brazing filler metals are widely applied, which serve as an industrial adhesive in the joining of dissimilar structures. With the continuous emergence of new structures and materials, the demand for novel brazing filler metals is ever-increasing. It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals. This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals, formability and processability, and overall cost. The basic properties of brazing filler metals refer to their mechanical properties, physicochemical properties, electromagnetic properties, corrosion resistance, and the wettability and fluidity during brazing. The formability and processability of brazing filler metals include the processes of smelting and casting, extrusion, rolling, drawing and ring-making, as well as the processes of granulation, powder production, and the molding of amorphous and microcrystalline structures. The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost. Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators. Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators. Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals, and solid solution structures contribute to the formability. By employing the proposed design guidelines, typical Ag based, Cu based, Zn based brazing filler metals, and Sn based solders were designed and successfully applied in major scientific and engineering projects.