Metrics are measurements that help you evaluate behavior or performance results, and measurement is what makes marketing a science, rather than a superstition. Metrics could be anything from the number of monthly page views on your website, to the number of likes on a social post, to the revenue made in the first quarter. Metrics matter because they are the indicators that let you know if your actions are changing the outcome. Did attendence to your quilting workshop increase after you ran a Facebook ad targeting all the quilters in your city? Look at the metrics, and you’ll know.