@kmk66 I take magnesium and also drink low sodium V-8 for potassium (should be over the day but I tend to have it in the am and magnesium in the evening).

Metoprolol will do nothing except to try to keep a lid on your heart rate. It isn't an anti-arrhythmic drug, so your heart WILL go into, and out of, AF.....on its own. At least, in the early 'paroxysmal' stage, that is what you can expect. Metoprolol only works to slow the HR and to make the heart beat less forcefully, meaning less oomph or pressure. Why cardiologists insist on adding more of it is beyond me, unless it is strictly to keep your fibrillating rate closer to 100 than upwards of that number. If you are breaking into AF now and then, taking 200 mg of Flecainide is often the remedy prescribed by physicians, keeping a 'pill in pocket' or PIP approach. And that's only IF you can tolerate flecainide...many cannot.
https://www.webmd.com/heart-disease/atrial-fibrillation/beta-blocker-medications-afib
My point in responding, though, is that too much metoprolol can be too much of a good thing. I can't begin to tell you how many AF sufferers report going into dangerous bradycardia when their AF advances and they need more and more metoprolol, to the point where when they break into NSR again, their rate plunges down into the very low 30's. My own was only 30 BPM in the ER, which is the 'keep alive' failsafe rate of the AV node. Metoprolol was shutting down my heart!!