From earliest beginnings in the 1990s, cataloging in school libraries is the product of three tasks--listing important details about an item (such as author, size, number of pages), selecting words and phrases that describe the item (such as subject headings, summary notes), and choosing numbers and codes that place the item on the shelf (such as Dewey Decimal Classification Number, Cutter numbers or letters, collection identification). Since the early 1980s, the presentation of cataloging has migrated from being listed on a card or series of cards to being presented electronically. In its electronic form, the MARC (Machine-Readable Cataloging) format or standard is the most widely used cataloging presentation standard currently used in school libraries. This article describes how metadata may change the way cataloging will be done in libraries. This article also examines the two types of descriptive metadata: (1) the Dublin Core; and (2) the Gateway to Educational Materials (GEM) and Gateway to 21st Century Skills/GEM Initiative. (Contains 1 figure.)