Some people here wrote Christians won't do it, but you would be surprised. There are exceptions...
Monogamy was the norm among Christians, However, in the context of the sickness of a wife preventing matrimonial intercourse, the founder of the Protestant Reformation, Martin Luther wrote: "I confess that I cannot forbid a person to marry several wives, for it does not contradict the Scripture. If a man wishes to marry more than one wife he should be asked whether he is satisfied in his conscience that he may do so in accordance with the word of God. In such a case the civil authority has nothing to do in the matter."
Thing is, Christianity comes from Judaism, and Judaism practiced it. It was especially common in rulers, not just because they were rich, but to forge pacts and alliances with other countries etc.
By the time Islam came into being, polygamy was still practiced among their contemporaries, even Christians. But some simply never got married, because of celibate etc.
Today some Christian denominations/sects practice it. Most secular laws in the west forbid it, and in that case they do it "in private", to avoid the (secular) legal troubles.
In more recent times you see for instance kings in Africa, convert to Christianity, but they happen to have like 15 wives or so, they make exceptions (not letting him marry more, etc).
However, a small group of evangelical Christians in the West numbering 50,000 persons practice Christian polygamy, believing that the Bible glorifies this form of marriage, citing the fact that many biblical prophets had multiple wives, including David, Abraham, Jacob and Solomon. Individual evangelical Christian pastors throughout Christendom have married more than one woman. The Presbyterian missionary Harold Turner acknowledged that the practice of polygamy was a cultural norm in some parts of the world, such as Africa, and cautioned against Western Christian missionaries imposing the foreign cultural norm of monogamy on the Christians of Africa as the latter would lead to the sins of divorce, leaving children without both of their parents, and remarriage of the divorced wife.