Salam. :]
Firstly, to the person who sent this,I apologize for taking such a long time to answer this question.
Check this post out for the daleels as to why gay marriage is prohibited in Islam.
Since we are at the topic of homosexuality, I just wish to bring up one matter. Every human being is tested differently and God wont test one beyond his capabilities.
Attraction felt by one person for another are most of the time innate - including when one is attracted towards another of the same gender. The feeling itself, since it comes naturally, is not sinful. Allah is just. However, it becomes sinful when it is expressed in actions - marriages & sexual acts- because it is prohibited by the religion.
To make it clearer, lets use fasting in the month of Ramadhan as an analogy. While feeling hungry and wanting to eat arent sinful, satisfying them before maghrib surely is. Get me? :]
Brothers & sisters, resisting self from the prohibited is a Jihad. May Allah reward the struggle and sacrifices with Jannah. Amin.