Are you...
>! A Trap?? (revised from a Strap, which is a weaker answer*cough* I mean it doesn't work.)

Reasoning:
>! "Be careful I'm dangerous, left how I'm read" <br>
>! Traps are generally dangerous.<br><br>
>! "Remove my first letter and I'll become music instead" <br>Rap is a type of music.<br><br>
>! "Switch my middle letters and I'm used as a cover" <br>Tarp, short for Tarpaulin, is used as a cover.<br><br>
>! "Leave me as a cover then take away my last letter, I'll become something flammable like no other" <br>Tar is very flammable.

Method:
>! Looked up types of music, found [this][1], used brute force.


  [1]: http://www.musicgenreslist.com/