Two biggies are ICE and CME - there was talk last year of a merger to create a super exchange.
Some info here:
It's a long, long story - first thing I'd do is read up on how/why there became a commodities exchange, learn it's purpose. Read some life stories of the many traders in that market.
Later you will find that specific commodities have different fundamentals, I mentioned copper only because in history it's price reflects world industrial usage (copper is used in many industries) and so it got called Doctor.
John Murphy had a good book that gave some insights on some of the metals (inter market analysis)
but there is a huge amount of information freely available.
Note that the bookie brokers' prices are usually reflective of market prices, with the usual caveats attached on spreads and liquidity.
The CRB is very useful in reflecting prices and demand for commodities worldwide.
Here is a little thinking to start off on:
Commodities prices generally reflect supply/demand - oil prices were in decline from a peak in 2008 at 140.00 per barrel to 26.00 - two years ago.
From that time prices have steadily risen, some would argue reflecting the more stable economic outlook.
The low occurred in mid Jan 2016 and then mid Feb 2016 a lower low - at a time when there was incessant talk of $20.00 per barrel.
On Oanda use weekly charts:-
XCU/USD - the low was mid Jan, no repeat the following month - the good doctor was indicating an improvement the patient's health