Some frames are made from magnesium or alloys with magnesium in them.Magnesium is very flammable so I won't ride them due to the risk I 'd catch fire....what was this thread about again? Oh nevermind.
That's sort of true. It's only flamable in powder or shavings...not frames or blocks.
This reminds me of all the old stories of why a VW engine catches fire so easy...I am sure it had nothing to do with plastic fule filters and pumping gasoline into a into the engine compartment!