Macos Mohave

I don't think you understood my reply. Your model is already Metal-ready. Mojave and Catalina will provide the drivers needed for Metal support. Your model already has the hardware. There is nothing to add. Just upgrade macOS.

You can upgrade your model to Catalina. Mojave is no longer available for models that are compatible with Catalina. You should be able to upgrade by following instructions here: How to upgrade to macOS Catalina.

Before You Upgrade macOS

1. Fix any problems before upgrading.
2. Run First Aid in Disk Utility while booted from your Recovery HD.
3. Backup. Make a bootable clone using CarbonCopy Cloner or use TimeMachine.
4. Be sure your startup disk has 18-20GB of free space during the installation.
5. Upgrade third-party software for compatibility. See App Compatibility Table - RoaringApps. If you have mission critical software, then DO NOT upgrade until you know that software is compatible with the version of macOS you are about to install.
6. Disconnect all third-party peripherals.
7. Download the installer which will be in the Applications folder. Quit the installer after it opens, then make a copy of the installer and save it in the Downloads folder. The one in the Applications folder will be deleted after a successful installation.
8. The download is large, anywhere between 5 and 9GBs. It takes time to complete. Be patient.
9. Double-click on the installer in the Applications folder. Click on the start button to begin the installation.

Note that your model is in the following list.

Mac computers that support Metal

MacBook (2015 and later)

MacBook Air (2012 and later)

MacBook Pro (2012 and later)

Mac mini (2012 and later)

iMac (2012 and later)

Mac Pro (Late 2013)

Find out if your Mac computer supports Metal in OS X El Capitan and later.

Metal is a graphics technology from Apple that allows the main processor (CPU) and graphics processor (GPU) to work together more effectively, providing faster and more fluid graphics performance in games and high-performance apps.