"Quantum Leap" is NOT a large measure. It's the transition of an electron between two quantum states. It's an incredibly tiny change. It's madly tiny.
No, all metal does not sound the same. Jesus. Yes, most of what's played on the radio sounds pretty samey, but most of that is really just awkward hard rock with a few metal elements thrown in there. Metal encompasses everything from crazy fast, noisy, rough sounds (see Norwegian and early-wave black metal) to clean and highly technical (lost of prog metal) to painfully slow and unnerving (Khanate).
No, young people communicating differently is not "the decay of English". Because you talk differently from your parents, who talked different from their parents, etc.
No, "literally" is not being used "incorrectly," unless you're a pedantic prescriptivist who thinks that there's some form of "proper English" that everyone is required to speak (completely ignoring the concept of "dialect," "idiolects," and "that is moronic"). Yes, it's annoying as holy hell to hear it used every third word, but the meaning is shifting to that of a generic intensifier. For historical parallel, "soon" used to mean "immediately." But, people kept using it so hyperbolically ("I'll do that soon [right away]") that the meaning has shifted to "in the near future" rather than "right this very second".
A bit less frustrating is "ye olde". When the printing press was introduced to England, the language still used the Thorn character (a voiceless "th" sound--like in "three," "through," "think," etc; contrast with "the," "this," "that"). But, the printing press did not have one; so, "y" was used in place of Thorn. Thus, "ye olde" would not be pronounce "yee old," but more or less just like "the old".