No problem at all! You will need to enable developer options in the Android Auto app on your phone. Find the AA app, then scroll to the bottom where it says “version and permission info”. Tap on that section about 7 times until you see a message saying that you have enabled developer options. Then go to the three dots in the right top corner and you will now see developer settings listed there. Open this and enable “unknown sources”. All your non-Google-playstore apps should now show up in your Android Auto, permitted they support AA that is (Metro music player does). Good luck!!