Perovskite-related metal halides exhibit unique structures and tunable optoelectronic properties that have enabled a wide range of potential applications including solar cells, light-emitting diodes, and radiation detectors. Two main focuses include understating the structure-property relationships and exploring advanced new materials with designable functionalities. In this talk, I will present our recent efforts in investigating metal halides using high pressure, focusing on the modulation of their structure-function motifs. Using in situ synchrotron-based and in-laboratory diagnostic tools, we investigated the evolution of the lattice, electronic, optical, and optoelectronic properties of various metal halides with different dimensionalities and revealed their structure-property relationships. Our findings deepen the understanding of fundamental mechanisms and obtain some new optoelectronic metal halides with emergent or enhanced properties.