How to make attach armor to player properly

I am trying to make armor attach to a player I tried to use weld but the armor move back a little when I start walking

Make sure the armor doesn’t have collisions, or you set up some collision groups to prevent issues.

Welds should work fine, you also may want to make it massless which will impact player movement.

I’m not sure of your exact issue, but you should try using RigidConstraints. They should be a lot easier to work with. Just add an attachment to the armor and also add a RigidConstraint. In the RigidConstraints properties, you can set Attachment0 to the one you just added to the armor and then use a script to set Attachment1 to one of the pre-existing attachments that roblox already has on the characters body parts. If the armor is rotated wrong or placed too far in a certain direction, use the move and rotate tool on the attachment that you added to the armor.