Hi all, i have just began trading on decentralized exchanges like IDEX and have a few questions. 

I am using metamask to transfer to  interact with the exchange but are my coins being stored on metamask?  and can i use my trezor to trasfer to and from the exchange.  I am trying to trasnfer some coins i just bought off of IDEX and am having trouble sending the transaction.  made me think the coins arnt actually being stored on metamask and that i need to first transfer them off of the exchange?

thanks all!