Brett Baty’s first-inning grand slam set the pace and the visiting New York Mets held on to beat the Atlanta Braves 8-5 on Monday in the opener of a three-game series. The Mets ended Atlanta’s nine-game home-field winning streak and improved their record against the Braves to 7-4. The Mets put up five runs off Bryce Elder in the opening inning. Elder (8-7) worked five innings and allowed seven runs on 10 hits, two of them homers, and three walks while striking out four. He allowed four runs on seven hits and one walk, and he struck out six.