A rectangular waveguide filled with uniaxial metamaterial is investigated in this presentation. The EM fields distribution of TE modes in such a rectangular waveguide are derived, and transmission characteristics are discussed. It is shown that the longitudinal component of the metamaterial permittivity tensor has strong influence on the direction of the phase velocity for TE mode waves. Particularly, not only backward waves, but also forward waves can propagate below the cutoff frequency of the waveguide.