WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
Apply urethane to the roof weld joint.
Install the roof weld joint reveal molding (1) to the roof.
Fig 1: Installing Roof Weld Joint Reveal Molding To Roof