Genesis 19:4-7 meaning

Sodom's sin is clearly revealed when the men of Sodom surrounded the house (v 4). The news of strangers in town had spread, and the men knew where to find them. They openly made known their intentions to assault the visitors sexually saying, bring them out to us that we may have relations with them (v 5). 

Have relations is a translation of the Hebrew word yada. Yada means to know intimately, and is often translated "know." The context here makes it clear their intent was sexual. Yada is used the same way in Genesis 4:1, translated as "had relations" as follows: "Now the man had relations with his wife Eve, and she conceived and gave birth to Cain." Yada being translated as "had relations" in Genesis 4:1 clearly means sexual intercourse, as the result of "yada" was that Cain was conceived and born. 

This proved Sodom's depravity (Genesis 13:13, 18:20-21). Men from every sector of the city and every age group, both young and old (v 4) were involved in the planned sexual assault concerning the two visitors. It seems there was an intent for the entire hoard to abuse them.

The Bible clearly condemns this kind of assault. It also consistently pronounces this kind of behavior as wicked (Leviticus 18:22,, 29, 20:1323; Romans 1:18-32; 1 Corinthians 6:9; 1 Timothy 1:10). 

Lot went out to them (v 6) to try to dissuade them from their wicked behavior asking, Please, my brothers, do not act wickedly (v 7). Wickedness can refer to moral depravity, immorality, idolatry, drunkenness, or rebellion (Deuteronomy 13:13; 1 Samuel 1:16, 2:12). Here the reference is to sexual assault of a mob of men upon two visiting men (2 Samuel 13:12; Romans 1:27). It is interesting to note that Lot anticipated their actions, but seems to believe he is immune from this treatment himself. This could have something to do with Abraham being his uncle. The town knew Abraham had a mighty band of well trained, armed men who had defeated four kings that had vanquished Sodom. Abraham had returned Lot to the city (Genesis 14). It might be that, up to the point, they did not want to mess with Abraham.