As the reverse process of relaxation, rejuvenation is the structural excitation process that can bring metallic glasses (MGs) to a higher energy state and usually increases their free volume. Here, using a dilution procedure conducted by randomly removing atoms from the modeled glass matrix, the degree of rejuvenation can be systematically controlled and the maximum rejuvenation threshold of MGs is identified. The structural relaxation is activated during the rejuvenation process and the dynamic balance between free volume creation and annihilation defines the rejuvenation ability of MGs. The highest degree of rejuvenation correlates to the flow strain of the materials and the structure is similar to that found in shear bands.