The majority of games you can claim immediately on steam are free to play games on the steam, app or browser.

Go to store on the menu in the drop down, select free to play here, you'll be able to browse and search every title that is currently free to download.

On steam, you can sort through to find popular games like Counter Strike, Global Offensive Team, Fortress two or War Frame.

You can also find free games through crowd sourcing sites and communities.

Free game finders is a community on steam.

That's a strong place to start.

You can also find various communities on reddit like R slash free games on steam or R slash game deals.

Okay, you can also find free games off of steam Stores like Humble Bundle, which offer pay what you want bundles and monthly subscriptions sometimes offer free games in their store.

Keep checking back to see when those deals appear.

If you have Amazon prime, you have access to Prime gaming, another option.

To get free games on a non steam platform, with a rotating catalog of free games and in game loot and bonuses.