“I need you to check with Metzger to see if he'd be okay if Tyler and I settled some old maters. He'll understand what I mean.”— Lara
Get permission from Metzger for gang war is a quest in Fallout 2.
Talk to Metzger and be as polite as possible in order to complete the quest. Then return to Lara for further duties.
Completing this quest unlocks the next quest, Find weakness in Tyler's gang guarding the church.