With the goal of enabling the design of liquid metal polymer composites (LMPCs) with desired electrical and mechanical properties while preventing premature dielectric aging and failure, the dielectric breakdown characteristics of LMPCs containing galinstan (GaInSn), barium titanate (BTO), iron (Fe), and mixtures thereof are investigated. The dielectric properties including dielectric loss (tan δ), partial discharge inception electric field (PDIE), and breakdown electric field (Ebd) are investigated. According to the study, LMPCs with a higher overall filler concentration tend to show higher tan δ, lower PDIE, and lower Ebd. The study also demonstrates that these dielectric properties vary by the type of filler even with an equally maintained filler concentration. This is due to the distinct filler conductivity, permittivity, and geometry that cause differences in the electric field distribution within the composites. To provide further insights into the observed experimental results, finite element analysis (FEA) models were developed and analyzed.