Licensing for applications

Is there a limit on the metrics monitored for all the application monitors like IIS and SQL?

Yes, for every application monitored, there is a limit on the number of metrics monitored within the application. The given limit is for a single monitor. 
Monitor
Type
Licensing Limit
Basic100 sites, 100 applications, 100 application pools. For additional monitoring support, contact support@site24x7.com 
Advanced
200 databases
Basic
100 containers, 100 images
Advanced
100 host instances, 100 message box hosts, 100 message box general, 100 orchestrations, 100 send ports, 100 receive ports, 100 hosts, 100 receive locations

You need to have a Windows/Linux agent installed to monitor any of the above applications.