We consider accurate simulations of metamaterial (MM) structures consisting of split- ring-resonators (SRRs) and thin wires (TWs). We employ electric-field integral equation (EFIE) to formulate the scattering problems involving these complicated structures. Accurate modelling of MMs translates into very large computational problems, which can be solved with the aid of advanced acceleration techniques, such as the multilevel fast multipole algorithm (MLFMA). We investigate various multilayer structures of SRRs as well as composite metamaterials (CMMs) constructed by the arrangements of SRR and TW arrays. In addition, we consider various disordering scenarios, where the unit cells are not placed perfectly and they are misaligned. This way, we investigate the electromagnetic properties of MMs when the arrays are defected. In this paper, we briefly report the accurate solutions of various real-life MM problems and present power transmission properties of these important structures.