The effect of electron interactions on cohesion in the one-band model is investigated using Gutzwiller's method and is found to give a lower cohesive energy than that obtained by Friedel, the difference being greatest for a half-filled band. This extends qualitatively to transition metals, the effect of electron interactions on the itinerancy of the wavefunction being greatest for a half-filled d band, and in the middle of the 3d series the elastic moduli, melting point and heat of fusion indicate a much weaker binding than expected from Friedel's model, which works well for the 4d and 5d series. From the size of this deviation is argued that correlation effects are crucially important in determining the electronic structure in the 3d series, resulting, for example, in the difference in electronic structure of iron and nickel and their response to a nontransition element impurity. Finally, the implications for the surface properties of the transition elements, in particular for their catalytic activity, are discussed.