In this you can identify all three mechanisms of heat tranfer. The following are the list of heat transfer in this case.
1) Through convection - From flame to metal pot.
If the flame is near to the pot, heat transfer happens through convection. The heated gas particles will go an be in contact with metal and then heat will be trnaferred to metal.
2) Through radiation - From flame to metal pot
If the flame has high temperature. radiation heat transfer can also happen.
3) Through metal pot - conduction throigh the metal
4) Through convection and conduction both to the water inside
5) Through convection - The heat will be tranferred inside the pot through convection involving water.
6) Through convection to the outer air from the boiling water surface
7) Through convection from metal pot to surrounding air if hot metal surface is exposed to air)
8) Through radiation from metal pot to surrounding environment (If temeperature is high)