There are many reasons for rape, but three are considered the most common. Since men (the OP specified men) are people and all people are different in motives, generally, no-one can say, It is this, or, It is that.
The first is because the man feels weak and impotent. This reason also applies to many child rape cases. He may come across as confident around women and even be married, but underneath he's seething with insecurities and wonders about himself. One of these deep-rooted insecurities may be his sexual performance, penis size, and so on. So he rapes in order to make himself feel virile, strong and, very importantly, to avoid rejection (the rejection would also reinforce his notion of his insecurities).
The second is revenge. Without going into too much detail because this could go for paragraphs, he has had trauma, bad experiences, constant rejection, by women, or -- and often the case-- his mother made him feel emasculated and dominated him as long as she could. This is the type that thinks women are 'whores' and his family life was probably far from comfortable. There may have been a divorce, a mistress, etc. and his view of women is now tainted two-fold by an overbearing, emasculating mother and another woman, who he deems a whore, in the picture, which may have been the cause of a divorce etc. He takes revenge on women by humiliating them and reinforcing his notion of them as sluts by deluding himself into believing 'they wanted it' as well as asserting his masculinity.
The third is the sadist. He is more often than not born this way. He experiences sexual pleasure from the humiliation of others and probably started with animals. He actively enjoys his victim's suffering and he becomes a serial rapist because, like a drug, he needs more and more to have the satisfaction he once achieved from simple forms of torture. His victims tend to die or he keeps them in captivity for a long time, maybe alongside others. This may or may not be co-morbid with one or both above.