Well boys like girls songs arent very complex and therefore they are fairly easy to interpret and I did a line by line but here is the basic summary a guy thinks he has found the love of his life until she leaves him he is hurt and angry and keeps his heart under lock and key so to speak then he meets a new girl he is hesitant to let her in after the first girl broke his heart but he quickly realizes she is very different and that going around with a chip on his shoulder closing everyone out because of one girl was stupid

It's too late baby, there's no turning around
I've got my hands in my pocket and my head in a cloud
This is how I do
When I think about you
I never thought that you could break me apart
I keep a sinister smile and a hold of my heart
You want to get inside
Then you can get in line
But not this time

*he is telling a girl persumably his ex that its too late to get back togeher the damage has already been done he didn't think she could hurt him like that and now he is a lot more gaurded with his feelings*

Cause you caught me off guard
Now I'm running and screaming

*he didn't think she would break his heart and now he is basicaly going crazy*

I feel like a hero and you are my heroine

*he is saying that after a hard day she is the only thing that makes him feel better and he is fighting the addiction to her*

I won't try to philosophize
I'll just take a deep breath and I'll look in your eyes
This is how I feel
And it's so surreal
I got a closet filled up to the brim
With the ghosts of my past and the skeletons
And I don't know why
You'd even try
But I won't lie

*ok well I'm pretty sure he is talking to a different girl now there is a definate shift here well he is just gonna "say it straight" so to speak and not give her an mixed meanings or cryptic messeges he is telling her he has had some trouble in his past and he doesn't know wh she would even attempt to love him*

You caught me off guard
Now I'm running and screaming

*now I think he is saying the new girls love caught him off gaurd he probably thaught he would never find anyone he loved as much as the first girl*

I feel like a hero and you are my heroine
Do you know that your love is the sweetest sin?

*now by hero I think he is saying he feels on top of the world instead of baring the wieght of it with the second line you get the feel that this is maybe a forbiden love*

And I feel a weakness coming on
Never felt so good to be so wrong
Had my heart on lockdown
And then you turned me around
I'm feeling like a new born child
Every time I get a chance to see you smile
It's not complicated
I was so jaded

*he has finally completly given in to his love for this new girl he has opened his heart to love once again "I feel like a newborn child" he is starting fresh with a clean slate and he doesn't have a care in the world other than her he realizes he acted foolishly after the first girl left him*

And you caught me off guard
Now I'm running and screaming

I feel like a hero and you are my heroine
Do you know that your love is the sweetest sin?

(I feel like a hero and you are my heroine)
And I feel a weakness coming on
Never felt so good to be so wrong
Had my heart on lockdown
And then you turned me around
(Do you know that your love is the sweetest sin?)
I'm feeling like a new born child
Every time I get a chance to see you smile
It's not complicated
I was so jaded

(I feel like a hero and you are my heroine)
And I feel a weakness coming on
Never felt so good to be so wrong
Had my heart on lockdown
And then you turned me around
(Do you know that your love is the sweetest sin?)
I'm feeling like a new born child
Every time I get a chance to see you smile
It's not complicated
I was so jaded