Last summer I got my metanium MGL hg and I love it. But this year when I got it out after winter and was messing about in the yard casting it, I noticed that is what noisy on the cast. Almost sounds like the spool is grinding on something. But it doesn’t seem to affect casting performance.  I’ve looked at the spool as well as where it sits and I see nothing wrong. What would this be?

I’d say take it apart and give it a good cleaning and re lube.  If you’re not comfortable, send it to someone who can.  

It sounds like your spool bearings need cleaned.

I had this same problem. Mine was still under warranty, so I returned it to Shimano.  It came back and developed the same problem. I had Chronarchs MGL’s that did not exhibit the same problem. I eventually sold it and replaced it with another Chronarch MGL. If you do a search, you will find other people who had experienced the same problem. 

4 hours ago, Rodney Smith said:

I had this same problem. Mine was still under warranty, so I returned it to Shimano.  It came back and developed the same problem. I had Chronarchs MGL’s that did not exhibit the same problem. I eventually sold it and replaced it with another Chronarch MGL. If you do a search, you will find other people who had experienced the same problem. 

 

This is exactly what happened to me, and it still does. I have to service this reel a few times per season to keep it working. I service my other reels a few times a decade lol.

I have cleaned and re-lubed the reel and still does it. I’ve got a met dc that needs to be deep cleaned so Ill just send this one along with it so they can look at it. Not good for a $400 reel to have this kind of problem 

It's common for these reels to develop some sound once they free up but not necessarily noise. I'd have to see it to diagnose.