Unlike bats wing which is performed purposefully, Bat Wings are the spreading and sticking of ones sack to the inner thigh. Usually happens at random, in summer months and is caused by the heat and persperation from the hey-nanner-nanner region.
Guy1: Dude, what the hell are you doing down there, have you got crabs or something?
Guy2: No, sorry man just have to adjust the bat wings.
To gain ones metal wings, the individual must ingage in sexual relations with a person or persons registered disabled with serious mobility disfunction.
With the excitement of the prospect of gaining the legendary 'metal wings', Bob did't hesitate in wheeling Sally to a quiet spot where he could happily penetrate her unabated.