Our aim is to improve the macroscopic description of wetting. We adopt the framework of the ''fluids with internal capillarity'' theory, for which the fluid-fluid interfaces are defined as zones (i.e. interfaces with a thickness), where lies a strong density variation. The continuum mechanics equations, considering the fluid-fluid interfacial zone, allow the concept of interfacial tension and Laplace's law to be rediscovered by limit processes. Following this modeling, we propose to characterize the transition zone between a fluid and a solid. We build a fluid model, with a constitutive law valid in the vicinity of a solid wall. Moreover, we estimate internal and external actions of this wall on the considered fluid by using a simplified molecular theory. We write out the system of equations and present some preliminary results for the peculiar case of a static drop.