We have investigated the photonic band gap and transmission properties of metallic photonic crystals (PCs) filled with liquid crystal (LC) in the terahertz region by using the finite element method and the finitedifference time-domain method. The calculations on the LC-filled metallic PC and metallic PC waveguide demonstrated that they can realize low-loss broadband terahertz tunable filters,which have a tunable range of about 110 GHz and extinction ratio larger than 35 dB.Moreover,the 3 dB bandwidths of the filters keep constant.The designed filters based on the metallic PC can greatly improve the performances in terms of loss,bandwidth and tunable region compared to those based on the LC-filled dielectric PC.