Metformin in either it's standard form or in slow release form (SR) still takes time in lining the intestinal tract, and as Liam1955 quite rightly says the timing when it's taken isn't generally that critical, though if you happen to be on 2 tablets a day, then it's best to spread the dosage out by taking one in the morning (with breakfast) and the other approx. 12 hours later with either dinner or the evening meal.
Skipping any meal isn't a good thing if you have diabetes, and it's easier to control your blood/glucose levels if you eat regularly and spread your food intake over the working day, if necessary eating less but more often.