A hypothesis for two-stage character of deformation under load via the simple shear scheme is suggested. At the first stage in the shear strain range , where - the strain parameter, the metal microstructure changes in the way similar to that during elongation. At the second stage at accidental multi-scale rotative motions, similar to turbulent motions in liquids, take place in the metal. This stage of deformation is the proper simple shear. The results of experiments are presented, which testify in favor of the suggested hypothesis.