Metadata Collection Interval is grayed in the adapter settings of VMware Aria Operations Management Pack for VMware Cloud Director.
VMware Aria Operations Management Pack for VMware Cloud Director 8.x
The Metadata Collection Interval (Minutes) cannot be changed currently. Changing this value was found to cause API failures from the VCD end. Therefore, it was disabled to reduce load on VCD server. Also note, metadata usually does not change very frequently, unlike metrics.