Regarding the German fortifications around Metz as defended 1944 consider the timeless verity of combat as enunciated by Dupuy # 6:
"Defenders chances of success are directly proportional to fortification strength."
Construction of the Metz fortifications even if DECADES OLD rather robust:
"The fortifications around Metz consisted of casemates, concrete barracks, infantry strong points, and concrete batteries, equipped with rotating steel turrets (100–150 mm). Each position was surrounded by several ditches, or concrete trenches, with shelters and observation cupolas. A large barbed wire belt, defended by machine gun and rifle positions, completed the defensive system."
Cross-sectional diagram of the forts as the American might have encountered at Metz. Fortifications as designed and constructed seventy years earlier but nonetheless strong fighting positions. Consisting of a moat, an infantry strong point and an artillery firing position. Underground living quarters and connection tunnels allowing for a dynamic and robust defense.
"Forts had usually several large blockhouse style barracks. These had 3-meter thick reinforced concrete roofs with 2-meter thick walls. They were partially buried under as much as 6 m (20 ft) of compacted earth. Underground tunnels connected all of the structures. The fort also had deep wide trenches, some as much as 9 m (30 ft) in both dimensions. They were also surrounded by a thick layer of barbed wire entanglements."
According to the calculations of the American military authority/historian/analyst fortifications of this type a force multiplier enhancing the combat capability of a given unit by 60 %!!
I MIGHT THINK TOO THE GERMAN USING LOTS AND LOTS OF LAND MINES!
No wonder why Patton got such a "bloody nose" at Metz!