A method is proposed to inhibit the leakage of electromagnetic waves on the surface of 2D photonic crystals using total internal reflection. The band structures of 2D metallic photonic crystals with different background mediums are analyzed. The band structures as a function of the filling factor are obtained via FDTD method. The metallic photonic crystals are composed of Cu columns. Two kinds of background media, air and PMMA, were selected in this study. The band structures of these two 2D square-lattice metallic photonic crystals were analyzed separately. The results indicate that the metallic photonic crystals filled with PMMA have a narrower first band gap and a lower second band gap than the metallic photonic crystals filled with air. A third band gap appears in the metallic photonic crystals with PMMA as the background medium when the filling factor reaches 0.70. This work provides a good reference value for the application of photonic crystals.