Yes, the device will work on Metro PCS, however, the device must be unlocked first.
In order to unlock the phone from T-Mobile, you would need to contact T-Mobile and request to unlock the Galaxy S6 Edge+.
Below, you can view the necessary steps needed to unlock a phone from T-Mobile.
T-Mobile provides mobile device unlock codes free of charge within two business days (or provides further information about timing) for eligible devices.
Device eligibility is determined as follows:
The device must be a T-Mobile device.
The device must not be reported as lost, stolen or blocked to T-Mobile.
The account associated with the device must be in good standing.
You have requested no more than 2 mobile device unlock codes per line of service in the last 12 months.
The device must satisfy all the Postpaid or Prepaid Unlocking terms outlined below.