How can an iceberg (temperature=0 celsius) have more energy than a burning match head (temperature=230 celsius)?

Temperature is the average energy of each particle and does not really give you an indication of the total internal energy.  That being said, total internal energy is the sum of all of the molecule's energy in a given object so it would make sense that an ice berg (having a huge number molecules at a lower average energy) would have more internal energy than a match head (having a much smaller number of molecules at a higher average energy).  Basically, the fact that ice bergs tend to be huge and contain much more molecules than a match head, means that ice bergs can have a larger total internal energy which means they store more energy.

I hope this helps.

They can measure  the amount of energy gained or lost