Although librarians hear and see the terms "metadata" and "identifiers" frequently in the current environment, many are not sure which topics these terms encompass or what metadata means to libraries. This article will examine identifiers and metadata in the digital world, especially those identifiers which can be used for continuing resources. The ISSN (International Standard Serial Number) and its metadata will be used as examples of how identifiers and metadata can help solve some of the challenges libraries face with serials and other continuing resources, such as identification, check-in, and obtaining records for library catalogs. Linking in the digital environment will also be discussed, including the challenges presented by resources that are available in multiple formats.