Thanks its a Sony LCD DVD xav-602bt player and a Mitsubishi Lancer. My current Nexus 5 doesn't send the metadata all i get is a blank screen but my old Galaxy S3 and my friends LG G3 does. The player has mirror link but I don't believe the 5x like the 5 supports that either. I have to wait and see I get my 5x this week.
Well I got my new 5x and unfortunately it's the same issue as my 5 in that it won't send Google Play music metadata but older non Nexus and iPhones do.
It's possible that Sony hasn't updated the firmware enough to support how Marshmallow handles things. The S3 and G3 are relatively older phones. iPhones may be a different case, since stereo manufacturers historically cater more to iOS users.
Mine kinda does in my Mazda CX9. It will send the first song info, but then never update unless I manually choose a different song with the phone. Using Amazon Music Player. I don't know if the problem is the 5X, the Amazon player, or the CX9.