“We are getting married but my fiance does not want a wedding ring. How can I change his mind?”
For starters, I don’t think this should be about changing his mind. Perhaps there is a reason that he does not want one. For example rings can be dangerous if you work in carpentry. It could be deeper underlying things such as not wanting to be tied down. If this is the case, you really need to speak. So start by finding out why he does not want a ring. It might be a perfectly acceptable reason.
Once you have spoken about it. You can explain how it is symbolic and traditional to exchange rings. If it is about style, you could show him a catalogue of mens wedding rings. It does not even have to be gold and perhaps you can have a matching one. You could also consider perhaps exchanging a watch in lieu of a ring. You do have options, but you need to find out why he does not want a ring first!
Good Luck and Congratulations!