Cellulose-based electronic devices show great potential for the development of advanced green electronics, such as digital resistive switching (RS) memory and analog RS artificial synapses. Previous studies on two-terminal devices have primarily used cellulose as a channel for the formation and rupture of metallic conductive filaments that directly govern the RS behavior. This means that cellulose has not yet played a central role in directly controlling the RS behavior in two-terminal devices. In this study, by combining density functional theory calculations with experimental investigations, we functionalized the porous cellulose layer using sputtered-metal atoms during the top electrode deposition process for (Ag, Cr, and Ti)-metal/cellulose/FTO structures. Digital RS behavior was observed in the Cr/cellulose/FTO structure, where the functionalized cellulose layer contained deep isolated trap states induced by adsorbed Cr atoms. In contrast, the Ti/cellulose/FTO structure demonstrated analog RS behavior due to the near-continuous transport of electrons through closely spaced shallow trap states induced by Ti adsorption. The difficulty in functionalizing cellulose with sputtered-Ag atoms facilitated the formation of Ag conductive filaments, which exhibited the typical digital RS behavior commonly observed. This study demonstrates that cellulose can indeed serve as an active and tunable layer for achieving desired RS modes.