This study aims at developing the conductive pastes consisting of room temperature vulcanizing (RTV) silicone and metal powder as matrix and filler, respectively. Electrical and rheological properties of metal - filled polymer composites are in general strongly affected by particle shape, side and dispersion state of the filler. In highly filled systems, particles tend to form very complex agglomerated structure which is easily changed when subjected to shear deformation. And the breakdown of agglomerated particles due to shear usually leads to the change of electrical conductivity of the composite. In this study, the effect of particle size and dispersion state of filler on the electrical conductivity of the composites are investigated to offer the selection criteria of conductive filler by measuring the rheological properties of uncured composites and the electrical conductivity of the cured composites. It was found that the type of metal filler systematically affected the rheological property, the susceptibility to shear and the degree of change of electrical conductivity of the composite. The effect of shear on the properties is more conspicuous in the composites containing large particle, indicating that both rheological and electrical properties can be improved by controlling the dispersion state at a given filler content.