A 4-aminothiophenol self-assembled monolayer (see image) is prepared on top of a Au(111) crystal, which is subsequently metallized by a nearly closed Pd overlayer of monoatomic height. Analysis of its structural setup and electronic properties reveals that the monolayer consists of a minimum of two molecular layers, and strong chemical interactions between the metal overlayer and the amino groups are found to play a decisive role in determining the overall electronic, and thus the transport properties, of the layer/metal contact.