Well I don't have a metal cage (yet) but I think the thing you should ask is how familiar with that kind of thing are you. Like if it's your first time trying something like that maybe you should get into the cage and used to it first while maybe trying it out slowly.
Like I'm thinking about that one as a possible choice, but I've never tried that kind of thing. So if I did order that I would def be easing into it myself.
That said, I believe Thumper has said it's like the most comfortable device he owns and I know he uses the plug. Sooo... Yea.