Then Make it clear that if you act upon it, that it is only you sleeping with another man and nothing else. If you do not feel comfortable, don't do it, it will make things awkward after and can be harmful.

Good luck~!

Go for it and enjoy yourself. I allowed my girlfriend to do the same, and it is, indeed the turn on of a lifetime. It will only make your sex life better at home.

If you have a very strong relationship and not the jealous type and of course if you want to try it, then go for it.
But as far as why men feel that this is a turn on there are many men who enjoy this.
Seeing thier girl moaning and groaning is pure exxtacy to some men, maybe they feel inadeqaute or they want you to enjoy better sex and are just voyuers.
swingers have done this for years and many do it for years, it is the joy of sharing and making her feel good (if she likes it)
Ask him why he prefers this and what is his reason for this.
If you do have sex with some one else rather it be one or two men always do it safely but see how he reacts after you have done this. He may be fully turned on and blow you away/Good luck

Set up a cameracorder in a room where only you and the man you are making love to. Record the love making as he pound on you and you moaning & groaning to his love making. Get in a position so that he will be able to see the man's penis moving back and forth in your vagina. Let him watch as that man give you good oral sex. Let him watch as you gives good oral sex. Take the CD home and let your boyfriend watch it, you never know til he witness another man making love to you if that he can stand for you to screw someone else. To some men, it is a big turn on, it will boost his love making with you. To other, it is a danger thing to do, because he is not ready for this kind of thing. He may think he is ready until he see just how much you are enjoying it. That is why 90% of married people cheats, and not being honest to their mates because they knows that their mates will not be able to face the true!!!!