Brokers & MetaTrader 4

 
Im interested in how MetaTrader 4 is affiliated with the brokers that offer use of this platform. It seems that every major forex broker offers MT4 yet you have to set up an account with MT4 which is a different account from the one you would set up with the broker if you used their platforms. For instance, if I were to set up an MT4 account through broker A who offers X spread for a given currency pair as opposed to Broker B with spread Y for the same pair, would my MT4 software show spread X having gone through broker A, and spread Y having gone through broker B? Do all of the attributes of whichever broker I use MT4 through just apply themselves to the trading platform or is there any other difference beyond when using MT4 between different brokers. I just want to get a clear picture of how the two are connected. Thank you for your replies!
 

in backtesting the broker you are logged in supplies the data

in not testing the same - you only can login to one dealer/broker and his rules apply and are used by MT4 or the EA's

 
meikel:

in backtesting the broker you are logged in supplies the data

in not testing the same - you only can login to one dealer/broker and his rules apply and are used by MT4 or the EA's

More accurately - the Market Properties and Account Info is supplied by the broker. The data is whatever hst file u have in your brokers folder or in the downloads folder, which are not necessarily the broker's (for example pressing download does not download from the broker but from MQ and it's inductive data from several sources).