Offshore wind turbine monopiles are usually analysed with a single eccentric load applied above the mudline, although the real environmental action is distributed along the structure as rotor thrust, tower wind drag and hydrodynamic wave load, and the balance between them changes with the sea state. The consequences of this idealisation for the foundation response have not been systematically examined. This study compares three load cases for a 5 m diameter monopile embedded 25 m in dense sand and supporting the NREL 5 MW turbine: a conventional single hub load, rated wind with a normal sea state (NSS), and extreme wind with an extreme sea state (ESS). Their effective load heights above the mudline were 125.0, 96.1 and 26.7 m (e/D = 25.0, 19.2 and 5.3). A three-dimensional coupled finite-element model in Abaqus, validated against FAST, ADAMS and OpenSees modal frequencies and the PISA Dunkirk field test, and an independent nonlinear p–y model were used. Responses were compared at equal mudline displacements of 0.10 m and 0.50 m (0.1D). In both models, the ESS case needed 3.1–3.5 times the horizontal load of the hub-load case at the same displacement, while carrying only 67–74% of its overturning moment. ESS loading moved the rotation point and the maximum-moment location deeper, reduced the maximum bending moment by 21–25%, and reduced the normalised toe reaction to about 0.3 times the hub-load value. The NSS case remained close to the hub-load case. These trends were consistent in both soil models, whereas absolute stiffness and the depths of the rotation point and maximum moment depended on the soil model. A single hub load is therefore adequate for thrust-dominated operation but misrepresents the load path, bending-moment distribution and soil mobilisation under wave-dominated extreme conditions, with implications for embedded-section design.