I overstayed my visa. Can I still apply for a green card through marriage?

Yes, if you're married to a U.S. citizen, you may still adjust your status (get a green card) even if you overstayed your visa.

 You’ll need to file Form I-130 (petition) and Form I-485 (adjustment of status) at the same time this is allowed for immediate relatives of U.S. citizens.

The overstay is forgiven for spouses of U.S. citizens if you entered the U.S. legally, even if your visa has long since expired.