Hi there,
I have the ATH-M50s and Klipsch Image S4 earbuds... and i do listen a lot to metal music. I haven't tried yet the DT 770, but i am planning to test them.
The two are really different. ATH-M50 gives you more detail in the highs, mid range and lower mid. However, Image S4's give you way more bass, in intensity and lower extension, but not necessarily in accuracy of the response . Problem is, i find both the M50 and S4 to lack in responsivess in fast pace passages, specially in the lower end (i.e. the double bass drum, palm mutes, bass guitar struck rapidly with a pick, etc...) the S4 are worse in that respect than the M50 though.
Even if both of them are low impedance, i find an amplifier is mandatory for optimal performance and bass response. On the go , i use the Electric-avenues PA2V2 (70$) linked with a Fiio Cable (L3 i believe) and at my office, i have the Musical Paradise MP-301 MK3 with 6L6 tubes. The PA2V2 has less background loise, but not the tube sound of course. The PA2V2 is quite satisfying none the less.