Polymer composites of poly(methyl methacrylate) (PMMA) and cuprous oxide (Cu2O), magnesium oxide (MgO), copper biphthalocyanine, iron (II) chloride (FeCl2), and iron metal were prepared by different filler-to-polymer percentages of 10, 20, 30, 40, and 50%. With increasing filler concentration, brinell hardness increases. Copper biphthalocyanine resulted in the highest hardness, and iron metal resulted in the lowest one. The electrical conductivity was found to increase with increasing filler concentration. The iron metal composite gave the highest effect, while the magnesium oxide composite resulted in the lowest one. The 50% concentration samples were subjected to electrical conductivity measurements at temperatures ranging from 25 to 100 degrees C. The electrical conductivity was found to increase with increasing the temperature.