You can glue metal to metal using an epoxy adhesive such as Loctite Epoxy Metal / Concrete. Other bonding agents for metal include Bostik Serious Stuff Liquid Metal, J-B Weld SteelStik Epoxy Putty and several others. Each has slightly different instructions but some general tips apply to many metal-to-metal bonding products.
Clean the two surfaces to be joined. Dry them thoroughly. Roughen the surfaces a little with emery paper if necessary.
Pull out the plastic piston plug or similar mechanism, where present, from the twin chambers to allow the two chemicals -- resin and hardener -- to mix. Select a nozzle snipping point -- where the nose cone is sealed -- that will produce material at the thickness required. Remove the end of the nozzle with a craft knife.
Activate the syringe, if present, by inverting it and withdrawing the plunge mechanism. Where a dual-chamber delivery mechanism is present, prepare to discharge resin and hardener independently and mix manually before application.
Apply beads of material, or “butter” the surfaces to be joined, depending on the physical characteristics of the bonding agent. Press the metallic surfaces tightly together and hold in place with pegs or other easily-deployed devices. Leave for about ten minutes, or longer, as specified on the full instructions leaflet supplied with each product. Metal to metal adhesion is achieved.
Wear gloves to prevent accidental metal glue application on fingers.
Before commencing the procedure, check the precise metals that can be glued together with each specific product.
Dispose of spent cartridges in accordance with local hazardous waste regulations.