A review of recent theoretical advances in the study of wetting phenomena is presented concentrating on the application of effective interface models for simple fluids. These models are particularly relevant for elucidating the fluctuation behaviour of unbinding interfaces, with a range of fluctuation regimes being predicted for critical and tricritical wetting. The prediction of a stiffness instability mechanism for critical wetting, caused by the presence of a position-dependent stiffness coefficient, is discussed and quantitative estimates for its relevance are provided. The failure of simple single field models to correctly recover mean-field correlation function behaviour is also demonstrated and an appropriately modified model is introduced to overcome this problem. Comparisons with Monte Carlo simulation results are presented, and a brief tour of the application of interface models to a range of materials and geometries is included.