I have acquaintances who are both male and female and I have friends who are both male and female and I have very close friends who are both male and female and I had one friend who was my ultimate friend, also my spouse. There are very clear cut boundaries and roles and my very close friends who also happen to be male were always very respectful of husband and my marriage as was I. I never kept company with any married or not married in any sort of compromising situation. The multitude of intimacies in a marriage operate on many levels from the physical to the non-physical and include many things that I would not share even with my closest female friend.
A marriage is an incredibly rich, nuanced tapestry and there are threads woven into it that are absolutely unique to the marital bond. You will never be able to capture them, create them, share them or experience them in anything other than a marital bond. . .you won't find them in the tapestry created with your friend and you definitely will not be able to find them or have them in an affair.
In our current society sex permeates and rots everything. The assumption is that two people of the opposite sex will automatically be drawn into sex really bugs me. This assumption permeates all discussion of teens and sex -- that they will be unable to avoid it, they are going to have it, so better contracept them. I say that is ridiculous, some will and some won't. Along with the idea that love must be expressed in sex. Love is free of sex. In marriage, sexual intimacy becomes a special language of love between the spouses. It is not the same in an illicit sexual relationship, nor is the love I have for my friends something I feel it necessary to express in that way and I have never felt that they did either.
I have been widowed almost a year now and my friends both male and female have been there. I have had long discussions. I have cried with them. They have hugged me and held me and held my hand and talked to me and loved me. None have offered sexual services (as evidently happens to some widows), none have made a pass, none have asked me on a date, nor intimated that they are interested in more, not even those I am closest with. Of my two very closest friends one is male and single and one is female and married. My male friend is a very good man, a very good practicing Catholic and I think him among the finest of men. I suppose it is possible with the boundary of my marriage removed something could develop but given that almost a year has passed and nothing has changed in our relationship, I don't think that is going to happen.
I don't know if it is something you have to experience, but the most intimate and dear friendships I have in no way compare to the relationship I shared with my husband, it is exponentially different and even my most intimate friendships pale in comparison to the marital relationship. And, that does not mean marriage is always smooth sailing and without slights and hurts and rough patches, but it is an entirely different thing. Having experienced both I continue to believe it is possible to have close friendships with members of the opposite sex that do not infringe upon the marital relationship, and I have to date had no experience that would indicate it was not possible.