Toilets, Sinks, Showers, Tubs and Disposals - Leak in pipe coupling under tub

Ok, once again I return to doityourself for some expert advice...Discovered a leak after taking a bath (that I only do a few times a year:). Of course, I had to cut a hole in the ceiling underneath in the laundry room to find it...The leak appears to be between the metal drain pipe and the pvc connection just above the pvc trap. There appears to be a metal slip nut on the top of the pvc pipe that connects to the metal drain. There is some play here and where I see some water coming from when tub is filled and draining. Is there washer or something that needs to be replaced to get this to not move at all and to tighen the seal where metal meets pvc at the slip nut...or is their some other sealer to use here...thanks, rick

I use JB Weld to seal everything.