Controversial take probably, but Hetfield’s tones have more to do with technique than anything else once you’ve got a reasonably high gain distorted tone happening.
From the amp side, I’d turn the ISF control all the way to the left (American side) and crank the gain up. Depending on the Metallica era you prefer you’ll need to adjust gain and midrange accordingly…generally older stuff is more scooped and distorted, newer stuff has more midrange and is slightly less saturated.
I noticed the amp also has cab simulation - I assume for direct recording. Big 4 x 12 cabs are a part of the Metallica vibe as well - you might want to try one of those through headphones and see how it sounds.
A small combo amp isn’t going to get you there no matter what, but that doesn’t mean you can’t get something workable.