Being a guy, you can definitely put on 20 pounds of muscle. There is a known honeymoon period for muscle building where during the first 6 months, you can make amazing gains but it'd taper off and it'd take more work afterwards to add additional muscle.
You can't out-exercise poor eating habits.
One thing to keep in mind too, is that at your starting weight, you also carry higher muscle mass, a natural byproduct of your weight and ability required to carry a body. It's easier to go from overweight to a solid muscle base than to go from very underweight and build the muscle.
You don't need to worry about putting on 20lbs of muscle (although this may happen naturally). Once you lose the excess weight, you may find it is already there. Strength training will be important in this journey but fat loss will be the goal