High-temperature metallic protective coatings have been widely used in advanced aero-engines, since they can protect hot components against high-temperature oxidation and corrosion by forming protective oxide scales, thus prolonging their service lifetime. Due to the effect on reducing oxidation rate of coating materials and improving scale adhesion, reactive elements were increasingly used for the modification of high-temperature protective coatings, especially for the modification of NiAl, which was a potential application material of metallic coatings used at ultra-high temperatures (≥1200 ℃). But up to now, the microscopic mechanism of reactive element effect was still in debate, as the influence factors of reactive element effect were too complex and the relevant action models remained incomplete. An overview on the research progress of reactive element modification in the field of high-temperature metallic protective coatings was given from the view of promoting selective oxidation, reducing scale growth rate and improving scale adhesion, especially for the alumina-forming alloys, typical materials of metallic protective coatings. The effects of reactive element modification on the microstructures, growth mechanisms, interfacial void formation and internal stress accumulation, etc. of oxide scale were emphatically analyzed. Moreover, interactions between reactive elements and impurities (e.g. C and S) were also focused on. Finally, deeper and more detailed future studies on the atomic scale are also anticipated, hoping to provide theoretical support for the development of ultra-high temperature metallic protective coatings.