The pilot reported that he was performing “touch and go landings” to get current. On approach, he heard a horn but thought it was the stall warning because it went off when he increased manifold pressure. But then he heard sheet metal grinding on concrete as the airplane settled. He applied full power and the airplane lifted off the runway. He then extended the landing gear, but the airplane’s left wing dropped, and the airplane impacted the ground. The airplane sustained substantial damage to the left wing and fuselage. The pilot reported the landing gear extended and retracted normally and the landing gear position lights and the landing gear unsafe warning horn functioned as designed. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.