My Quick Study “From black holes to strange metals” (Physics Today, June 2012, page 68) mentioned that the resistivity of an ordinary metal varies quadratically with temperature. I was specifically referring to the contribution from electron–electron interactions; that is the quality that can be directly compared with strange metals, whose resistance is thought to be due to electron interactions. Most ordinary metals receive many contributions to the resistivity and, indeed, the part due to electron–electron interactions may not be dominant until very low temperatures.