Best Answer: I've never heard of this band before you posted your question. I listen to the song and while I can't tell you what the lyrics mean (though I'll try below), I can say that this group's style is very much like the group of my era, Queen.
Their music stands alone, as it's theatrical (like theater show tunes) or an anthem. There are stories or statements made in FUN's music, especially their songs "We Are Young", "All The Pretty Girls" and "Carry On".
With that said, "my lips could build a castle" needs to be broken down. Look beyond the word "build". Lip Service is to speak. Freedom of speech. Speaking so much and it falls on deaf ears, but what is being said, continues to be said over and over and over again, and only then does the spoken word build. Did the songwriter feel that he has something important to say, so much so that it could make a change or make a difference. One also has to look at the word "castle". Most castles were built as a fortress to protect what was within the walls of the castle. What is the songwriter, through words, trying to protect? Freedom or a way of life maybe?
After listen to the song with lyrics only, I thought the song sounded like a cry to battle, then I searched for and watched the official video for the song "Some Nights" Imagine my surprise when I saw the video uses civil war effects for the video. In the end, is war worth it? Did anyone consider the horrors of war? Does battle achieve what we thought we were fight for. Most of the time . . . no.
FUN. A great band . . . thanks for introducing me.