While adding an ESX/ESXi host for monitoring, you can choose to auto-discover the virtual machines running on that host. These machines will be added automatically as individual monitors in the Site24x7 web client and their metrics collected.
Alternatively, you can also choose to exclude certain VMs from being auto-discovered. Specify the name of the VM under the field Exclude Virtual Machine if its name contains (as shown in the image below) to prevent unnecessary VMs being added for monitoring.