**4. Conclusion**

The chapter elucidates the importance of sheet metal joining by forming (plastic deformation). The technique developed so far have immense potential and significance to join similar and dissimilar metal sheets without melting, which allows achieving substantially greater joint efficiency than conventional sheet joining methods. The impact-based solid-state techniques, EMW, VFAW, and LIW share a similar mechanism to join sheet metal, but they differ in the welding energy sources they utilize as indicated by their names. In the roll bonding, the overlapped sheets are joined by joint plastic deformation; the squeezing action of rollers creates sufficient pressure at the interface to create a bond.

The joining by forming methods provide consistent joint quality, high repeatability, and higher production rates; which are the prerequisite factors that industries look for. The processes are environmentally friendly, as there is no emission of heat, radiation, or smoke during the process. Hence, it is feasible to use and develop these forming methods to join sheet metals.
