Metformin's effect is to lower blood glucose by a few points - it does this by interfereing with the liver adding its own created glucose to the blood. I've never used it so have no personal experience, but those on these forums who have seem to get slightly different reductions. This is most noticeable when someone stops metformin: BG will typically rise a little. Your husband, if he's thinking about stopping metformin, should discuss that with his GP or diabetic nurse.
There are a number of different views around on remission - I stick to one that says it's normal BG levels, no medication, no symptoms, for a reasonably long period of time - eg a year. There are other views that say it's two HbA1c results under 48 three months apart, without glucose lowering medication. Obviously one is easier to achieve than the other.