how to set metric on ubuntu 18.04

i have ubuntu server 18.04 i configure squid on it squid is running ok and no issue at all i have two lan card one from LAN network and other from ISP provider i want to out the trafic from ISP lan.but its out the traffic on LAN how i do this .i try to set metric wiht ifmetric command but its con't work when i set metric than i check from ifconfig command it show metric same for both network means 1 for both . please help me