these kinds of friendships work best for me when both of us are in committed relationships, and the chance of the intense feeling turning into sexual activity is the least likely.
i have had friends, both str8 and gay, for whom I felt such a close bond that i could confide in them things i would not confide even to my SO. sometimes, the feelings were intensely sexual, even with str8 guys, but there was no point in getting physical. i've had two str8 friends who told me that they had never felt sexual attraction to another man, but that something about me had made them aware of such feelings for the first time. we could be easy around each other even with that tension in the air, because we understood that neither of us wanted to jeopardize our primary relationship.
others were str8 guys who were interested in the emotional side of being gay, what it felt like. one was a guy who had a gay brother he wanted to reach out to, but who was hurting so bad that he didn't trust him. i think his intense attachment to me was based on his being able to talk to me and share affection with me in the way he couldn't, but longed to, with his own gay brother.
if i feel this kind of close bond with another guy is safe to express, it's hard for me to hold back the love i feel. i think my willingness to express it seems to make forming a bond easier for the other man. hugging and kissing on the cheek and other casual physical contact, even if it's prolonged, seem natural a lot of times, too. for me, tho, kissing a man on the lips is reserved for openly sexual love. that limit helps me define where some boundaries lie.