Finding The Right Words For A Wedding
Word of Congratulations for a Wedding

First, introduce yourself. If it is a medium to large sized wedding, many people are bound to not know you. Say your name and your relationship to the newlyweds.
Then, follow up by saying something like "I am so glad to see so many of your here tonight"
Go on by saying how nice the ceremony was or how touching it was.
Talk about the couple. Mention how nice they look together, how well they get along, etc.
Remember to make sure your speech is coherent, has a beginning, a middle and an end, just like any speech would.