These are the 5 core KPIs/metrics. If you measure and monitor with the "zeal of a zealot", it will transform your company and reputation. Even if you've never been measuring anything except how many or what kind of calls you receive, these are excellent metrics to start measuring to establish a base line for your organization.
Metric "discipline" is needed. Initially you or your organization may look "bad". It is often that way at the beginning. Sooner or later someone will ask for metrics. Some smart senior leader will ask for these KPIs/metrics. You are better off to identified these KPIs/metrics now so you can begin making progress and improve your numbers and trend lines.
If you do not have service level agreements today, there is a great whitepaper on the Giva web site about how to develop them and slowly introduce service level management to your organization. See https://www.givainc.com/wp/implementing-service-level-agreements-slas-writing.htm
Download the webinar slides: Metrics For IT Help Desk & Customer Service Organizations