We present the Empirical Interscale Finite Element Method (EIFEM), a variant of the standard FE method tailored for modeling multiscale heterogeneous structures in both dynamic and static nonlinear analyses. In essence, EIFEM is a domain decomposition method based on the Localized Lagrange Multiplier (LLM) framework, and complemented by model reduction techniques at the subdomain and interface levels. This method addresses key limitations of conventional multiscale frameworks by introducing an interscale variational formulation which establishes a direct correspondence between coarse-scale nodal forces and fine-scale stress fields. Unlike traditional nested local-global approaches, such as the widely used FE-2, EIFEM eliminates the need for iterative coupling, offering superior computational efficiency and straightforward implementation within standard finite element codes. A salient feature of EIFEM is its use of hyperreduction techniques, particularly the Continuous Empirical Cubature Method (CECM), which enables the efficient evaluation of the nonlinear terms . This capability is especially critical when modeling unit cells exhibiting highly nonlinear force-displacement responses, like the unit cells representing metamaterials with negative stiffness. Another key ingredient for capturing nonlinear behaviors is the representation of energetically “bubble” modes as internal degrees-of-freedom in the coarse-scale model. We show that the EIFEM is versatile across multiple scales, from unit cells and laminates to full-scale components like wings and fuselages. We also demonstrate that, as the coarse-scale mesh is refined, the coarse-scale response converges to that obtained with classical first-order computational homogenization, with each EIF element acting as a surrogate for a unit cell.