Surface metallization of the liquid crystal polymer (LCP) substrate will play a vital role in a large variety of potential technological applications in the high-frequency and high-speed 5G era. However, the pretreatment of surfaces is a major issue in the polymer metallization process. A facile green and mild surface oxidation method is proposed for the fabrication of flexible, stretchable, compressible, for enhanced metal-LCP interfacial adhesion. The surface oxidation process is accomplished by exposing the LCP substrate to the ultraviolet light-activated chlorine dioxide (ClO2) radical ambiance. The chlorine dioxide radical will chemically alter and modify the LCP substrate surface to promote increased adhesion of the metal and LCP layer during the lamination and electroless plating process. Moreover, flexible metal-LCP substrates are obtained based on the electroless deposition of metal (copper, nickel) on the LCP films. For the case of Cu-LCP substrate, excellent metallic conductivity of 2.6 × 107 S m−1, and excellent fatigue resistance under various deformations are shown. Adhesion strength of the modified LCP was enhanced by increasing the oxidation temperature and time. This work also provides a successful strategy for the pretreatment of other polymer substrates used for the selective metallization with precise patterns.