Gallium-based liquid metals are emerging materials for soft electronics with their fluidic compliance, low toxicity, metallic conductivity, and outstanding thermal conductivity. Especially, liquid metal particles (LMPs) mixed with polymeric matrix have demonstrated promising application potentials for soft and stretchable electronic applications including stretchable integrated circuits, capacitive sensors, dielectric elastomer actuators, and thermal management materials. This review highlights methods to prepare LMPs, control and manipulate LMPs within the polymeric matrix to meet the demands of different functionalities. Furthermore, we summarized recent advances by utilizing LMP composites to enable different stretchable electronic applications. It is believed that LMP composites will serve as important enabling materials for the development of electronic skins, stretchable electronics, smart textiles, and next-generation human-machine interfaces. A comprehensive and timely review of the recent progress in LMP composites is expected to inspire further exploration and innovation in stretchable and multifunctional electronic systems.