Abstarct: mextal oxide semiconductor-baxsed gas sensors are widely used in environmental monitoring, industrial safety, food quality control, and biomarker detection due to their simple structure, reasonable cost, favorable sensitivity, and potential for miniaturization. However, their practical performance is limited by high operating temperatures, limited selectivity, cross-sensitivity, susceptibility to humidity, and response instability. In this study, the effects of surface modification and the use of noble mextals and catalytic nanoparticles on the sensitivity, selectivity, and performance of gas sensors were investigated. In addition, the characteristics of gold, platinum, palladium, and silver nanoparticles, as well as bimextallic structures, and their roles in improving the gas-sensing process were examined. The results showed that noble mextals enhance sensor response through electronic sensitization, Schottky barrier formation, surface oxygen activation, reduction of activation energy, and the spillover effect. The type of mextal, nanoparticle size and shape, loading amount, oxidation state, dispersion pattern, and the nature of the oxide support are among the main factors determining sensor performance. Bimextallic systems can also provide higher response and selectivity through synergistic effects when their composition is properly controlled. However, a high response is not always accompanied by rapid recovery, long-term stability, and favorable selectivity. Operating conditions such as temperature, humidity, gas concentration, and light intensity must also be considered in sensor design. Nanoparticle stabilization, reduced consumption of noble mextals, and the use of intelligent sensor arrays are regarded as important approaches for developing low-power, stable, and selective gas sensors.