The barbecue at Metropolitan on Lorimer Street was it's usual tranny-treat yesterday. Boys and girls from all corners of the 'burg descended to imbibe $8 pitchers of Bud and chow down on free hot dogs and hamburgers. The BBQ at Metro has become quite the scene these past few summers: the number of non-'burgers dropping in has transformed Metro from neighborhood hang-out to Sunday destination. Trannies agree, summer Sundays at Metro > Sunday tea at the Blue Whale + the Sunday party at Garden of Ono. Faces in the crowd . . . wave-making NY-designer Prabal Gurung . . . Tuesday's GLAAD Summer Series host Matthew Maddox . . . a deeply-ginged GOOLIE Adam Shapiro . . . Park Avenue Peerage girls' favorite accessory Luigi Tadini . . .