Another product that can be used is SEM 39537 Weld-Bond Adhesive. It's used by body shops to adhere fiberglass and plastic panels to metal substrates.
Here's a quote from their MSDS sheet:
39537 WELD-BOND ADHESIVE is a non-sag, two component methacrylate adhesive system formulated to bond metal surfaces without the use of an external primer. 39537 provides long working times (45-60 minutes) allowing body shops to correctly position parts for proper alignment. This adhesive contains glass beads to insure adequate bond line control. 39537 is an easy to use 1:1 adhesive that forms resilient bonds and maintains its strength over a wide range of temperatures. 39537 is suitable for bonding a variety of substrates especially automotive grade cold rolled steel. Recommended substrates include steel, galvanized steel, e-coat, aluminum and stainless steel.
I used it on the hood and a headlight bucket of our 2001 Adventurer in 2007. Everything was still holding fine when we traded it off in 2013.