As some people have already said, "opus" means "work (of art)." And seeing as Imagine Dragons writes their own music, I think this song is about someone who got famous on their own and then started to gave in to their own fame and became a figurehead of sorts.
So, I'm going to start with the chorus because the chorus almost always holds the main point of the song:
It's not a picture perfect life
Not what I had in mind // These two lines refer to the lifestyle of someone famous, and how it's not perfect at all
Let me write my own line // This refers to the fact that the narrator wants to write their own music instead of preforming the music of others.
I've got this place
That I've filled with empty space // This would refer not to a physical space but the "place" in the artist's head where they used to write music.
Oh I'm trying not to face what I've done
My hopeless opus // The opus that's mentioned wouldn't be a song but the artist themselves, hopeless because they aren't really famous anymore but rather just someone who displays the work of others.
I'm in this race and I'm hoping just to place
Oh I'm trying not to face what's become of me // "What's become" of them is that they've started to not be themselves anymore, and they don't want to face that.
My hopeless opus
Now, to the first verse:
Hey Mr. cage man let me get a fresh breath // "Mr. Cage Man" would probably refer to an agent or someone who's pressuring the artist into not being themselves. The artist wants a fresh breath so they can start writing their own music again.
Cherry bomb head strong I could fake my own death // By faking their own death, the artist would be free of the constraints put on them and they could write their own music.
Hey Mr. fate man shuffle me a ninth life // They're asking for a "ninth life" so that they can become someone new and write their own music.
I've been wrong, go long
Throwing me a sharp right // The sharp right would be the sudden change from writing their own music to preforming the music of others.
Next:
Hey Mr. safe man hustle me an okay // If "Mr. Safe Man" hustles them an okay, they'll know it's safe to go back to writing their own music. This refers to the fact that it would be the safe thing to just keep preforming the music of others.
I could slide take a dive take it for the home team // "I could slide" means that they could lose their fame. I'm honestly not sure what the other things mean.
Hey Mr. postman slip me one more green note // They want to keep getting paid even if they go back, so they're asking the postman to give them one more "green note" or paycheck.
I've been low hit the floor looking just to make broke // They've been low probably as a struggling musician before they became famous. "Hit the floor" would be in the present, which is a metaphor for what would happen if they lost all their money. Again, I'm honestly not sure what the other stuff means.
In total, I think this is a song about how musicians feel pressure to stop being true to themselves once they become famous. It's very possible that Imagine Dragons themselves were pressured into preforming music not written by them, but they write their own music for the most part and it always shows through in their songs.
As some people have already said, "opus" means "work (of art)." And seeing as Imagine Dragons writes their own music, I think this song is about someone who got famous on their own and then started to gave in to their own fame and became a figurehead of sorts.
So, I'm going to start with the chorus because the chorus almost always holds the main point of the song:
It's not a picture perfect life Not what I had in mind // These two lines refer to the lifestyle of someone famous, and how it's not perfect at all Let me write my own line // This refers to the fact that the narrator wants to write their own music instead of preforming the music of others.
I've got this place That I've filled with empty space // This would refer not to a physical space but the "place" in the artist's head where they used to write music. Oh I'm trying not to face what I've done My hopeless opus // The opus that's mentioned wouldn't be a song but the artist themselves, hopeless because they aren't really famous anymore but rather just someone who displays the work of others. I'm in this race and I'm hoping just to place Oh I'm trying not to face what's become of me // "What's become" of them is that they've started to not be themselves anymore, and they don't want to face that. My hopeless opus
Now, to the first verse:
Hey Mr. cage man let me get a fresh breath // "Mr. Cage Man" would probably refer to an agent or someone who's pressuring the artist into not being themselves. The artist wants a fresh breath so they can start writing their own music again. Cherry bomb head strong I could fake my own death // By faking their own death, the artist would be free of the constraints put on them and they could write their own music. Hey Mr. fate man shuffle me a ninth life // They're asking for a "ninth life" so that they can become someone new and write their own music. I've been wrong, go long Throwing me a sharp right // The sharp right would be the sudden change from writing their own music to preforming the music of others.
Next:
Hey Mr. safe man hustle me an okay // If "Mr. Safe Man" hustles them an okay, they'll know it's safe to go back to writing their own music. This refers to the fact that it would be the safe thing to just keep preforming the music of others. I could slide take a dive take it for the home team // "I could slide" means that they could lose their fame. I'm honestly not sure what the other things mean. Hey Mr. postman slip me one more green note // They want to keep getting paid even if they go back, so they're asking the postman to give them one more "green note" or paycheck. I've been low hit the floor looking just to make broke // They've been low probably as a struggling musician before they became famous. "Hit the floor" would be in the present, which is a metaphor for what would happen if they lost all their money. Again, I'm honestly not sure what the other stuff means.
In total, I think this is a song about how musicians feel pressure to stop being true to themselves once they become famous. It's very possible that Imagine Dragons themselves were pressured into preforming music not written by them, but they write their own music for the most part and it always shows through in their songs.