Materials subjected to extreme shock compression experience a sequence of distinct regimes, each governed by different underlying physical mechanisms. This paper explores these transitions, beginning at the weak shock limit (WSL), where ambient shear strength is exceeded. Beyond the WSL, increasing strain forces electrons into progressively higher energy states. Upon reaching the shock melting pressure and beyond, materials undergo structural changes that culminate at the strong shock limit. At this point—approximately three times the melting pressure—electronic contributions dominate the material response, leading to reduced compressibility and the onset of electron degeneracy pressure. A theoretical model is presented to quantify this transition, showing that the threshold pressure depends on the free electron density. The findings highlight a critical relationship between ambient material properties and the nonlinear compression behavior under shock. This work underscores the importance of incorporating pressure-dependent physics into high-strain material models