The memristor has long been presented as the fourth fundamental circuit element alongside the resistor, the capacitor, and the inductor. As the future of computing heads toward neuromorphic circuits, there has been a renewed interest in the modeling and simulation of memristors which have emerged as promising key components in the design of these systems. Despite such critical applications, very few models have been presented in the literature that allow for the automated and flexible integration of memristors in different simulators. In this article, three different models of the memristor are presented using the modified nodal analysis (MNA) formulation technique. Each stamp is tested and compared with a theoretical model of the memristor. Simulations are also performed on a memristor-based active high-pass filter circuit to demonstrate the accuracy of the model.