How do I delete files that are greyed out?

Some images on the external drive appear to be defective, but I can’t delete them since the trash icon is greyed out. How do I fix that?

Is trash greyed out just for those images or for other healthy files too? Select a defective image and press Command + I to get info. Check if you have permission to read/write or its locked.

Thanks for responding.
All the images are greyed out and locked. When I tried to unlock images, I get the message, “…Is on a Read-Only Volume and Can Not be Unlocked.” How do I go about unlocking them? Thanks again,