The rules are very clear. Irons are not allowed in staterooms because they are considered fire hazards. I'm sure some people bring them despite the rules, but they're prohibited.
They're also heavy, and in the opinion of at least one male (me), completely unnecessary. Many others will answer with news of all sorts of aerosols that apparently do the job adequately. So does hanging stuff in a steamy shower.
Our preference is to back exceptionally light, bring no irons, curlers, spray cans or duct tape, and use the ship's laundry to refresh the things we bring. It's not that expensive, and being able to pack light is worth a few bucks.