95% of keys are made of brass, thus they're not magnetic. There is a few minority of keys that will be steel, but mostly are not. In saying that, Nissan keys are brass.
Be careful that no glue gets on any of the discs inside the lock. Otherwise it can make them stick and make it hard to unlock your car. It would then have to be either pulled apart, or carefully shoot some thinners or carby cleaner down the lock(try not to get it on the paint) to dissolve the glue.
This is not a practice that locksmiths use for the obvious reasons.