Being faced with digital libraries containing images and video content, means are required that characterize the content for efficient access. In addition, the confluence of media content which is distributed over a number of content providers requires a common and standardized way for searching the content. The usual solution consists in the employment of metadata which describes media content. Among others, issues that arise concern the kind of metadata to be used, how it is to be represented, and how it is to be integrated into the architecture of a portal for accessing the distributed digital archives. The methods presented in this paper have been implemented in the context of the project Gateway to Archives of Media Art (GAMA for short). The objective of this project is to establish a portal for online access to some of the most important digital archives and libraries on media art in Europe.