Here are some tips on how to repair metal with JB Weld. Whenever I use JB Weld to repair metal I like to put some extra metal into the joint to give it extra strength. Another good idea when using JB Weld is to do a lot of sanding to make sure the metal is clean so the JB Weld glue can stick to it. Also make sure you use the original 2 part formula for maximum strength. That is how to use JB Weld for metal repair.