An interpretation can be that the band is just having fun at a club, they just are throwing all their issues away and just having fun.
[Intro]
Ooh woah
[Verse 1]
Damn, now all the pretty teens and fake IDs around me
Where did they come from?
Oh, we'll never look like all the models in the movies
We'll never know
[Chorus]
But tonight, call your friends down
We're on our way now
And I feel like shouting, oh, I feel like shouting
Oh, tonight, it don't matter who you're from
Tonight we're 21 under all these lights
[Refrain]
(Hey)
I put my heart, I put my soul, I put my life in it
Look at me now
(Hey)
We're feeling dumb with coke and rum, we raise a glass to it
The underdogs
Oh oh-oh oh oh, oh oh oh oh
(Hey)
I throw my fingers to the ceiling and I won't give in
Look at me now
[Verse 2]
Wait, give me a minute, just a minute, get my focus straight
They're looking bored
When did all my friends turn into fake IDs and skinny jeans?
I don't belong
[Chorus]
But tonight, call your friends down
We're on our way now
And I feel like shouting, oh, I feel like shoutin'
Oh, tonight, it don't matter who you're from
Tonight we're 21 under all these lights
[Outro]
(Hey)
I put my heart, I put my soul, I put my life in it
Look at me now
(Hey)
We're feeling dumb with coke and rum, we raise a glass to it
The underdogs
(Oh oh-oh oh oh, oh oh oh oh)
(Hey)
I throw my fingers to the ceiling and I won't give in
Look at me now