Using the time dependent density functional theory calculations, we investigate how the optical response in Aluminium nanorod dimers evolve as a function of different tuning parameters such as gap distances (3-14 angstrom), structural configurations (compact, hollow and a combination of both) and relative spatial orientations (parallel and axial linkages). We found that the position and amplitude of the gap plasmons are continuously modified with decreasing gap distances in the case of nanorod dimer composed of compact structures, and below 6 angstrom, the electron tunnelling emerges in agreement with recent experiments. We have also investigated the gap plasmon modifications by placing a conducting molecule in the inter-particle gap region and found the molecule short circuits the junction and decreases the optical enhancement. (C) 2018 Elsevier B.V. All rights reserved.