One difficulty in understanding Christian morality is the difference between covenants. Morality comes in different forms. Sometimes, a thing is always right or wrong. We cannot, for example, say that because we are no longer under the law, therefore it is ok to murder. But other things are only wrong under a specific covenant. Can we eat pork, for example? An Old Testament Jew would have to say no, pigs are unclean. A Christian, however, can say we have been freed from the law, and multiple passages in the New Testament explicitly declare food choice to be a thing relative to the individual.
Because of this, many Christians erroneously question the legitimacy in using the Old Testament in discussions of morality (and some even go so far as to say the Old Testament is now worthless). "That's just the Old Testament, find it in the New!" they say. However, although Leviticus does deal a lot with moral laws such as the aforementioned prohibition on pork, which have been explicitly repealed by the Old Testament, it's clear that it also deals with things that are always immoral.
In Leviticus 18, several things, such as incest, bestiality, homosexuality, adultery, and child sacrifice are all mentioned, and the Lord tells Israel plainly that these are the very reason God is driving out the previous inhabitants of the land.
It is a great blessing that incest, bestiality, and burning children alive are not especially desired in our culture, but adultery is gaining speed, and homosexuality is so popular that some people claim the mere refusal to bake a cake for a gay "wedding" is homophobic and discriminatory.
Sadly, many Christians have fallen for this con, and they claim that since Leviticus is Old Testament, it is not valid for modern Christians. But aside from numerous verses in the New Testament that are clearly opposed to homosexuality, Leviticus 18:24-25 clearly tells us that God is punishing the nations themselves, who were not under the law, for these very sins.
As an ex-gay myself, I am beyond grateful that God no longer requires the same punishments for homosexual sin that He did in ancient Israel. Nevertheless, we can be sure that He is going to judge every individual after their deaths by what they have done during their lives. For the saved, this will be a lot more pleasant, as our sins were nailed to the cross. Nevertheless, God does promise that our works will still be judged (1 Corinthians 3:15), and that disobeying the least of commandments, and teaching men to do likewise, will result in being called the least in Heaven (Matthew 5:19). Thus, Christians should be advised not to follow the current trend of the culture. This will make us unpopular with man, but God will be pleased.