In this chapter, we deal with the application of electric, magnetic, and combined field integral equations (EFIE, MFIE, and CFIE) to analyze electromagnetic scattering from arbitrarily shaped three-dimensional perfectly conducting bodies in the frequency domain. In Section 2.1, a parametric surface model is described and the procedure of parametric patch generation is given. A set of basis function which was first proposed by Wilkes and Cha [2] is defined on a parametric sub-domain. In Section 2.2, the electric field integral equation (EFIE) formulation is presented. In Section 2.3, the magnetic field integral equation formulation is derived. In Section 2.4, the combined field integral equation is given.