Can I use a logo without copyright?

Could you elaborate on the legality of using a logo without copyright? I'm curious to understand if it's permissible to freely utilize a logo that doesn't have a copyright attached to it. I've come across some designs that appear to be unprotected, but I'm unsure if I can legally incorporate them into my branding or promotional materials. I'd appreciate any clarification on the legal implications of such an action, as well as any potential risks or considerations I should be aware of before proceeding. Thank you for your assistance in this matter.