A phenomenon of intense transmission of light has been observed from optical response to subwavelength structures in metal film. Using numerical simulation, an incident plane wave propagates toward a thin film of silver with a subwavelength slit and groove. This thesis explores parameters, such as slit-groove distance, location of placed molecules, and molecule resonance, which affect the transmission of light through the slit. It is shown how the eigenenergies of the system vary with slit-groove distance. Two scenarios were investigated; a) molecules placed inside groove and b) molecules placed inside slit. It is found that the most dramatic effect on transmission by molecules is with molecules inside slit.