Is there anything I can do to strengthen my metatarsal bone after surgery? >

Follow MD's guidance. Definitely discuss what is activities are safe or not for your particular surgery with your surgeon. In general, most healthy bones heal in about 6-8 weeks. Eating healthy and doing your prescribed rehabilitation will help strengthen your healing bone after surgery.
Time. Bone normally takes 6 weeks to heal. If internal fixation is used, healing is usually faster. As a rule: for each day you are immobilized( (cast, boot, surgical shoe) it take two additional days to recover (bones, tendons, ligaments) to get back to normal. It is important to increase activity gradually. Discuss in detail with your foot surgeon. Dr l.