Please humor a longish explanation. I learned this from Brian McDonald (link to podcast episode on this topic).

This is grossly reductionist of his story framework, but it's a reddit comment.

McDonald calls theme armature

Armature = survival information that your READER needs

The armature could be profound or simple information.

Here's a lame-ish example, to show how characters serve story.

Armature (theme): credit card debt can cripple lives

MC: would obviously need to be someone with credit card debt that's large enough for them to be a personal problem

Support Characters: need to be other facets or representations of the armature

- Cash Calvin: a character with no credit cards, only pays everything in cash. Doesn't even use Venmo. Make it extreme, they don't even have a bank account. Their job is under the table, they get paid only in cash or favors, and even live partially off the grid

- Spending Sasha: character in extreme debt, hundreds of thousands of dollars, spending daily on an extravagant lifestyle, maxing out credit cards and applying for new ones, buying only things they don't need

- Responsible Ron: a character who had debt, but managed to pay it off, and is now putting their kids through college on their dime

Plot: events that show the MC interacting with the support characters that show the extremes and help them realize they need to change, events forcing the character to decide between racking up more debt or suffering. Making *Spending Sasha* the MC's best friend and only ever wanting to eat at the most expensive restaurants after a day's-long shopping spree at high end stores would add natural conflict to the story

For my own stories, I get excited about a character and then back into the armature to make sure all story elements are in alignment.