Hi the cold water in my house can be a horrible taste. Very metallic tasting and the water flow in my shower is a trickle. Can anyone help

City or well water? Well water metallic taste is almost always iron.

My bet's on a well,
the water flow in my shower is a trickle
Try this. Shut the water off and pull the cartridge, Check the inlet ports for trash and clean. Now place a pan over the open valve and turn the water back on for a minute to flush out the supply. You should have a strong stream when doing so. Reassemble and test. If that works do it on all affected taps, good luck, Tom