The primary metric at the article level - a count of the number of times an article has been cited. There are three large, interdisciplinary databases that collect times cited:
Scite - want to see more about the context for your citations? Search Scite (by author, title, etc.) and its algorithm calculates whether collected citations are considered positive, negative, or neutral. You can also download an extension for Firefox, Chrome or Safari to view Scite information while using Scopus.
Page views and downloads are considered 'emerging metrics', but are quickly gaining acceptance, particularly as an early indicator of impact for articles.
Institutional repositories, including our own repository, also tracks these metrics. See here for more details on our repository, or contact Chris Lewis, the digital repository coordinator, directly for more information.