Another few hints:
- Understand basic FM techniques
- Modulate the FM intensity/depth with an envelope or fading LFO or one-shot
- Set OSC2 to silent and pitch up significantly higher than OSC1 (e.g. +24/+36). Then use LFO2 (fork mode) to modulate OSC1
- Try odd values/combinations for modulation speed/intensity
- Stepping through integer values (LFO depth) one by one also let’s you explore unexpected sonic territory
- Use all kinds of LFO waveform for modulation
- Start from a clean OSC waveform (there’s a few ways to achieve sine waves also)
- What sounds nice in low key breaks apart/glitches/aliases in higher regions often
Edit: Some FM Metal Sheets I posted a while ago somewhere else
Edit 2: It’s sometimes useful to have an idea of the sound you want to create. Think about the physics of metal objects and how they sound when being hit hard (metal to metal – lots of harmonics aka noise on the hit) or softly (cleaner tone, ringing, …). Then from initial impact to the tone (bell resonating long, deep and harmonically clean), metal sheets more dirty, rattling, broken … and so on. Analog FM being a bit unpredictable at times can still yield very nice results for the same reason.