Dr. Metz is the town doctor, and—Mrs. Woodcliff is his receptionist. Dr. Metz recommends that Jack have his nose fixed and eat iron-fortified cereal to help his nosebleeding condition (7.18). He's a man of science: he shows Jack how iron-rich the cereal is by crushing some up and holding a magnet to it, drawing out the iron flecks (7.18).
But he's also a man of business: Dr. Metz will only take cash in exchange for his services, and not any of the home-canned fruits or vegetables that Jack's Mom offers to exchange. Dr. Metz represents the future of Norvelt: less community; more cold, hard cash.