In this paper, we will provide an overview of our theoretical work on the role of metamaterial covers in dramatically enhancing the wave transmission through a subwavelength aperture over a perfectly conducting flat screen. It is well known that a low-permitivity or a low-permeability grounded slab may support surface polaritons. In our problem these natural modes are exploited to collect and redirect the impinging radiation into the tiny hole and to reshape the radiation pattern at the exit side of the screen towards an observer. The sum of these two effects may potentially lead to a dramatic increase in the total power transmission through the aperture. Moreover, we show how this effect may be further increased and optimized by employing bilayer covers with "conjugate" materials, i.e., materials with oppositely signed constitutive parameters. In some earlier works, we have indeed utilized such a coupling to induce a compact "interface" resonance, suggesting several microwave and optical applications. Here, the same resonant phenomenon can lead to the transmission enhancement together with a reduction of the required cover thickness. We provide some insights into the physical basis of this effect, and we speculate some potential applications.