Not being sure what you are trying to do or what you are picturing above, so here goes...
First you have one lead grounded to a painted piece of metal and I have no idea what the other end is connected to. If you want to find the resistance of say your negative ground cable, completely disconnect it from the vehicle, set the meter to ohms and place a lead on each end. Hopefully you get next to zero as that will indicate you have a good ground wire.