Research metrics are measures used to quantify the influence or impact of scholarly work.  Some examples of this are bibliometrics (methods to analyze and track scholarly literature), citation analysis, and altmetrics (a more recent set of alternative methods that attempt to track and analyze scholarship through various digital media.)

Journal metrics attempt to quantify the quality or influence of a given journal for purposes of comparison.  
 
The Journal Impact Factor, also known as Impact Factor, is the oldest and most widely used measure. Its use is often criticized for having a too-short window for analysis (two years) and failure to recognize differing expectations of citation rates among disciplines.
 
Important factors to consider are the time frame of the calculation and whether or not the metric includes all items in a journal (e.g. letters or news) or just the "citable" items. Measures that include all items tend to penalize journals that publish a variety of document types.

Journal Impact Factor (Web of Science) = number of citations to a journal in the current Journal Citation Reports (JCR) year to items published in the previous two years, divided by the total number of scholarly items (articles and reviews) published in the journal in the previous two years.

A journal may advertise its impact factor on its website. This claim should be verified in JCR in WoS Database

CiteScore (SCOPUS) = citations to a journal in a given year to documents in that journal from the previous three years, divided by the total number of documents (not just scholarly documents) published in the journal in the previous three years.

A tool that provides quantitative measurements of the visibility and influence of scholarly publications. It is based on the citations that publications have received in Google Scholar, and it includes metrics such as the h-index, h-median, and five-year citation count.