In actuality sodomy or homosexual behavior and gay marriage are two totally separate subjects. However this article will attempt to briefly show what scripture teaches about them.
Here are the scripture passages having to do with what we today call homosexual behavior.
Leviticus 18:22 "You shall not lie with a man, as with a woman. That is detestable."
Leviticus 20:13 "If a man lies with a male, as with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them."
Romans 1:26 "For this reason, God gave them up to vile passions. For their women changed the natural function into that which is against nature.
27 Likewise also the men, leaving the natural function of the woman, burned in their lust toward one another, men doing what is inappropriate with men, and receiving in themselves the due penalty of their error."
Deuteronomy 22:5 "A woman shall not wear men’s clothing, neither shall a man put on women’s clothing; for whoever does these things is an abomination to Yahweh your God."
1 Corinthians 16:13 "Watch! Stand firm in the faith! Be courageous! Be strong!"
In plain English Leviticus 18 and 20 say that a man must not have intercourse with a man. In the Greek in Romans 1:26 scripture indicates that a man must not have anal intercourse with a woman. Then verse 27 says likewise a man must not perform the same act with a man. The act of anal intercourse is sodomy. God does not make arbitrary law. Every Law of God has a purpose. This is a Health Law as it is meant to protect one from disease. I do believe this also includes the medical procedure Fecal Transplant. This should be examined in the light of God's Law. I think that it is also forbidden for the same reason as anal intercourse since the results can be the same.
In 1 Corinthians 16:13 the Greek for "be courageous" actually says, "act manly". There are several scriptures that express the idea that men should behave as men. When you combine that with Deuteronomy 22:5 the idea is that men should not dress as or behave as women. Since there is no set rule this is one of the few rules that can actually change based on the practice of the day. The point is still that men and women dress as is appropriate for their sex.
God's marriage is always between one man and one woman. There are many examples where a man had many wives, but even still in those situations a man had a separate marriage with each wife. A scriptural marriage contract is between one man and one woman. I have not spent a lot of time researching government marriage. There is a difference between God's form of marriage and that of the state. God's marriage is based solely on his moral law and never changes. Government's marriage is based on man's changing laws. From what I understand the state began issuing marriage licenses to give approval to marriages that God's morals would never allow. So the state began licensing marriages to allow for scripturally immoral marriages and then over time convinced Christians to also seek a license. Tax breaks and social security likely helped. Licensing may also have been created to offer some official stamp of approval for non-Christians. When speaking of God's marriage with state officials you should make them aware of which marriage you are referring to, God's marriage or the state's.
It should not be any surprise then that state marriage would evolve with the morals of the people living in the state. The state's marriage is not God's marriage. God created His form of marriage and He is the only one who can regulate it. The state can create any sort of license it wishes. It has no right to dictate God's marriage and some may ask why Christians should be partaking in state marriage. It is immoral at it's root. Why should one expect state marriage to be moral?
That is what scripture says. That does not include all the behavior that one might find between men or women for what society calls homosexuality or lesbianism. If you practice any of the other behaviors then my admonition is to consider those who might not be able to handle it. Remember Christians are to consider the weaker brother. If you are a Christian then you might consider helping or educating in a Christian manner those who do not understand some Christian freedoms.