How can I get a reports with customised metrics to suit my business requirements?

If you require business-specific metrics to be derived from Tickets in your account, you could make use of the Ticket Activities Export feature within Freshdesk. Using this feature, you could extract ticket information as a JSON file into your BI tools and thereby extract metrics from the ticket activities.

This way, you could create custom reports containing any metric from ticket activities, based on your business requirements.