Metoprorol 25mg/day, will this lower blood glucose level? not sure what "masking" of bg symptoms mean.

Hard to tell: 25 mg can have different effects in different patients, so it is hard to tell how you specifically are going to feel. Metoprolol doesn't lower blood glucose level, it will "mask" some symptoms of low blood glucose level. Usually, low blood glucose causes tremor and sweating, and metoprolol blocks exactly those symptoms.

In diabetes: If you don’t have diabetes, then this isn’t a concern. If you do, metoprolol may block some insulin release and lead to high blood sugars and poor diabetes control. However, especially in type 1 diabetes, it may block some of the symptoms of hypoglycemia (low blood sugar) like a racing heart and tremors, thereby masking hypoglycemia. Because hypoglycemia may be dangerous, patients are cautioned.