Metadata has become one of the fundamentals for digital library projects worldwide in recent years. With reference to the global trends of metadata development, this paper adopts comparison as the research methodology to explore the current metadata application and progress attained by the National Digital Archives program (NDAP) in Taiwan. Through this comparative study, four findings are in focus. Firstly, metadata applications by NDAP involve a rich diversity, including various communities, themes, data types, and data functions. In addition, the selected metadata standards by NDAP projects are primarily structured ones. Secondly, based on the strategy of parallel employment, multiple metadata standards are customized and interwoven for the applications of NDAP projects. Thirdly, metadata descriptions in NDAP projects are mainly focused on thing, person, and geo-spatial objects. Lastly, several common core sets of metadata, either on the thematic or on the community basis, have been gradually developed for metadata interoperability.