To have access to the full list of metrics available for Facebook Ads, you can check it in the Custom Reports

​RAW (taken directly from Facebook Ads)

Adds to Cart (GA4)

Adds to Cart Conversion Value

Clicks

Frequency

Impressions

Initiate Checkout

Initiate Checkout Value

Leads

Leads Value

Link Clicks

Mobile App Purchases

Mobile App Purchases Conversion Value

Outbound Clicks

Purchases

Purchases Conversion Value

Reach

Spend

Website Purchases

Website Purchases Conversion Value

COMPUTED (calculated from raw metrics based on Facebook Ads definitions)

Average Purchase Value

Cost per Add to Cart

Cost per Initiate Checkout

Cost per Lead

Cost per Purchase

CPC (All)

CPC (Link)

CPC (Outbound)

CPM

CTR (All)

CTR (Link)

CTR (Outbound)

Order Rate (Link Clicks)

Revenue per Click

Revenue per Impression

ROAS