In this paper, we present a non-overlapping domain decomposition method using integral equations in the frequency domain for the resolution of wave scattering from metallic objects. The objective is to use multi-domain modelling to process multi-scale structures. This method is flexible thanks to an independance between sub-domains and relying on the local resolution of these sub-domains. Moreover, the convergence is improved compared to a classical resolution. This method is achieved for predicting radar cross-sections, studying antenna sitting on large platforms and EMC applications.