Journal (or Publisher) metrics address the prestige that publications carry. They attempt to quantify the importance of a particular journal in its field, usually via an algorithm that takes into account the number of articles published per year and the number of citations to articles published in that journal.
While these metrics do tell us something, researchers in a discipline will have the best sense of the top journals in their field.
Tool for Journal Metrics:
SJR (SCImago Journal Rank) measures the "average prestige per article" and is based on the idea that not all citations of your work are the same.
Journal Impact Factor measures the frequency with which the average article in a journal has been cited in a particular year or other defined time period using data from Journal Citation Reports (see JCR box on this page)
h-index - refers to how many times at least h articles in a journal publication are cited at least h times each. For example, a publication with five articles cited by, respectively, 17, 9, 6, 3, and 2, has an h-index of 3.
Other tools include: CiteScore (only available through an institutional subscription to Scopus), Eigenfactor and Article Influence Scores (only available through an institutional subscription to Journal Citation Reports)