Despite decades of work, strange metals that defy Fermi liquid theory challenge our understanding. In this talk I will discuss properties of such phases of matter in systems with a global U(1) symmetry and discrete translation symmetries. I will show that the low-energy theory must have a very large emergent symmetry group -- larger than any compact Lie group. I will revisit standard Fermi liquid theory from a modern point of view of characterizing its emergent symmetry and its associated anomaly. Many, if not all, non-Fermi liquids will have the same emergent symmetry group/anomaly as a Fermi liquid (even though they could have very different dynamics). Such phases - dubbed ersatz Fermi liquids - share some (but not all) universal properties with Fermi liquids. I will discuss the implications for understanding the famous ``strange metal" physics observed in experiments in some condensed matter systems. Combined with a few experimental observations, I will show that these general model-independent considerations lead to concrete predictions about a class of strange metals. The most striking of these is a divergent susceptibility of an observable that has the same symmetries as the loop current order parameter.
