Most people understand what the lie angle on their irons is. And most understand the impact of a lie angle that is too upright or too flat on their accuracy. But it’s not at address that the sole needs to be square to the turf; It’s at impact, and the body’s position at impact is very different to what it was at address.
At address you need to have an good athletic posture that will allow all the parts of your body (hands, wrists, arms, shoulders, upper body, hips, and legs) to work through the swing. Your club then needs to have a shaft length and lie angle that works with that swing allowing the club to be delivered at the the best position at impact. There are over 50 variations of Lie Angle and Shaft Length. The swing is very dynamic. You need a Fitting when you’re buying Irons.