Strong　optical　excitation　of　plasmonic　nanostructures　may　induce　simultaneous　interband　and　intraband　electronic　transitions.　However,　interaction　mechanisms　between　interband,　intraband,　and　plasmon-band　processes　have　not　been　thoroughly　understood.　In　particular,　optical-heating-induced　lattice　expansion,　which　definitely　leads　to　shift　of　the　Fermi　level,　has　not　been　taken　into　account　in　plasmonic　studies.　Here,　it　is　shown　that　plasmonic　bandedge　shift　is　responsible　for　the　optical　modulation　on　the　boundary　between　plasmonic　electron　oscillation　and　interband　transitions　via　investigations　on　gold　nanofilms　and　nanoparticles.　Strong　optical　excitation　induces　transient　depletion　of　the　conduction　band　just　below　the　Fermi　level　through　intraband　transitions,　while　the　subsequent　lattice　heating　induces　transient　thermal　expansion　and　hence　lowers　the　Fermi　level.　Both　effects　reduce　the　threshold　for　interband　transitions　and　therefore　push　the　plasmonic　bandedge　to　the　red.　These　discoveries　introduce　a　first　correlation　between　plasmonic　response　and　optical　excitation　induced　thermal　expansion　of　lattices.　The　revealed　Fermi-level　adjustment　mechanism　allows　alignment　of　electronic　levels　at　the　metal-semiconductor　interfaces,　which　applies　to　all　conductive　materials　and　renders　reliable　physics　for　the　design　of　plasmonic　or　optoelectronic　devices.