You're half way correct..

If something is drawing lightning means there is a greater potential between those objects..

Your gate is already a lightning rod .. What is missing is an alternate path to ground other than through your auto gate earthing..

Since your auto gate is already being struck by lighting the solution is to ground the body..

so run a bit of copper tape to the body of that auto gate connect to a copper rod deep into ground as close to the auto gate as possible..

That should provide the alternate path to ground than your auto gate wire ..

Edit * qwerty223 is right .. I'm just putting his answer in another way..

This post has been edited by Richard: Dec 28 2016, 06:10 AM