Nonequilibrium hot carriers near the interfaces of semiconductors and metals play a crucial role in catalysis, chemical reactions, water splitting as well as optoelectronic processes. In addition to excitation by light, such hot carriers can also be generated due to quantum mechanical effects in tunnel junctions. The tunnelling behavior is extremely sensitive to the immediate property change of a medium placed in the tunnel path, which holds great opportunities for the development of tunnelling-based devices for the dynamical control of plasmons or the detections of environmental changes with high sensitivity. Here we will discuss hot-electron excitation in electrically-driven plasmonic nanorod metamaterials and their applications for light emission and gas sensing, including hydrogen and oxygen gases. Electrically-driven plasmonic nanorod metamaterials comprise a fertile platform merging photonics, electronics and chemistry, opening up opportunities for developing electron tunnelling-based nanoscale devices for light generation and modulators and chemical sensing.