In this paper, we describe a model to simulate the dynamics of a microactuator. The model is based on a finite-element discretization which gives a monolithic description of the strong coupling between the mechanical, electrostatic, and fluid fields. It therefore allows the computation of the nonlinear dynamic response of a microactuator. The methodology also leads in a natural way to the fully coupled linearized equations so that computing vibration behavior becomes feasible. In this paper, we also show how the model can be reduced in order to significantly decrease the computation costs while retaining a good accuracy even when nonlinear effects are significant. The proposed method is validated for a microbridge for which measurements found in literature were used.