Abstract: The development of stretchable conductors with high deformation, conductivity, and thermal conductivity using liquid metal (LM) has sparked widespread interest in the fields of flexible electronics, electromagnetic interference (EMI), and multifunctional materials. However, fabricating desirable shielding materials by directly coating LMs on soft polymer substrates remains a challenge because of the huge surface tension and weak wettability of LMs. In this study, Ga-based composite paste is prepared from a mixture of Ga and diamond nonmetallic particles through ultrasonic fragmentation. At various temperatures, the resulting LM composite putty (LMP) exhibits soft and hard properties and can thus be molded into specific shapes according to application needs. In addition, the composite can be easily coated onto polymer substrates, such as thermoplastic polyurethane (TPU) elastomer. The fabricated LMP–TPU exhibits an impressive shape deformation capacity of 1100%, demonstrating exceptional tensile properties and achieving electromagnetic interference–shielding effectiveness of up to 52 dB. Furthermore, it retains an ultrahigh conductivity of 20000 S/m, even under a strain of 600%. This feature further makes it a highly competitive multifunctional material.