Can i use a verizon iphone 4 for t-mobile?

I want to buy an iphone 4 from verizon and i have tmobile i know you need a micro sim card and i can get it

You cannot use a iPhone from Verizon on T-Mobile because Verizon is a CDMA carrier and T-Mobile is a GSM carrier.
I advise you to buy a factory unlocked iPhone from Apple. This will be a GSM phone ready to be used on any GSM carrier that will sell you a SIM for it. You should be able to buy this SIM from T-Mobile. Contact your T-Mobile rep or their customer service for more information.

No, the iPhone 4 from Verizon is CDMA only and not compatible with T-Mobile
you also can't get the discounted/contract price if you are not getting verizon service

you CAN use a Verizon iPhone 4s or 5, which are both world phones, if you get the iPhone 4s unlocked (the 5 comes unlocked)

First you need to unlock your iphone