font-metric-overrides.csv is a CSV that contains font metric overrides for all fonts available from Google Fonts.

font,ascent-override,descent-override,line-gap-override
"/ofl/poppins/Poppins-Regular.ttf",1.05,0.35,0.1
"/apache/opensanscondensed/OpenSansCondensed-LightItalic.ttf",1.068847656,0.29296875,0
"/apache/chewy/Chewy-Regular.ttf",varies by OS,varies by OS,varies by OS
...

Include font metric overrides to your stylesheets:

h1 {
    font-family: "Poppins", "fallback for Poppins";
}
@font-face {
    font-family: "fallback for Poppins";
    src: local("Arial");
    ascent-override: 105%;
    descent-override: 35%;
    line-gap-override: 10%;
}

For more information on using font metric overrides see Improved font fallbacks.

font-metadata.csv contains various font metadata (for example, ascent/descent/line-gap, glyphs widths, and UPM) that is relevant to generating font fallbacks.

Yes! Check out these tools:

Non-framework tools:

• Fontaine: Fontaine is a library that automatically generates and inserts font fallbacks that use font metric overrides.
• Capsize is a font sizing and layout library. Capsize provides an API for getting information about various font metrics.

Framework tools:

• @next/font: Starting in Next 13, next/font automatically uses font metric overrides and size-adjust to provide matching font fallbacks.
• @nuxtjs/fontaine: Starting in Nuxt 3, you can use nuxt/fontaine to automatically generate and insert matching font fallbacks into the stylesheets used by your Nuxt app.