"Message in a Bottle (From The Vault)" is Swift's admission of fascination and admiration for a new potential lover. Although frightening, this new infatuation carries with it hopes of being true love. The song seems to be connected thematically to "Come Back...Be Here," which talks about Swift struggling to have a long-distance relationship with someone. It is rumored that the subject of both songs is Harry Styles, whom Swift dated toward the end of 2012.

A "message in a bottle" is a form of communication used by castaways looking for rescue. Similarly, Taylor uses it to express her readiness for commitment to someone seemingly far away for now, specifically in "London," conveniently being a city in Harry Styles' home country. With the outro's lyrics differing from those in the chorus, it seems that this song is an actual "message in a bottle" to her potential lover.

The song's pop sound, with an upbeat tempo brought on by drums and a guitar, is very familiar to songs on Swift's 1989. The similarities between this song and ones on 1989 make sense, since this is the first track Taylor wrote with Max Martin and Shellback. Both producers contributed on many songs in 1989, most notably "Wildest Dreams," "Style," "Blank Space," and "Shake It Off."

Lyrics-

I know that you like me
And it's kinda frightenin' standin' here waitin', waitin'
And I became hypnotized by freckles and bright eyes, tongue-tied

But now you're so far away and I'm down
Feelin' like a face in the crowd
I'm reachin' for you, terrified

'Cause you could be the one that I love
I could be the one that you dream of
A message in a bottle is all I can do
Standin' here, hopin' it gets to you
You could be the one that I keep, and I
I could be the reason you can't sleep at night
A message in a bottle is all I can do
Standin' here, hopin' it gets to you

These days I'm restless
Workdays are endless, look how you made me, made me
But time moves faster, replaying your laughter, disaster

'Cause now you're so far away and I'm down
Feelin' like a face in the crowd
I'm reachin' for you, terrified, 'cause

'Cause you could be the one that I love
I could be the one that you dream of
A message in a bottle is all I can do
Standin' here, hopin' it gets to you (It gets to you)
You could be the one that I keep, and I (I)
I could be the reason you can't sleep at night (At night)
A message in a bottle is all I can do
Standin' here, hopin' it gets to you

How is it in London? (London)
Where were you while I'm wondering (Wondering)
If I'll ever see you again?
You could be the one that I love, mm-mm
And now I'm standin' here, hopin' it gets to you

'Cause you could be the one that I love (Yeah, yeah)
I could be the one that you dream of
A message in a bottle is all I can do
Standin' here, hopin' it gets to you (It gets to you)
I could be the reason you can't sleep at night (You can't sleep at night)
A message in a bottle is all I can do (Yeah, yeah)
Standin' here, hopin' it gets to you (Yeah, yeah)

You could be the one that I love
You could be the one that I love, I love
And now I'm standin' here, hopin' this gets to you