If you've played the engie you know how important the setup period is and how rare metal can be.
You can really help by choosing engineer class and then using your 200 metal during the setup period to help build his sentry/teleporter. Then change class to your preferred player which will suicide you but it will leave behind your spanner which is worth 100. You should then have just enough time to respawn and make your way to the frontline (maybe via a teleport you've helped build) ready for kick off.
So next time you play a round with a setup period think how you can give a gift of 300 metal to your friendly engie