Good info shared @pr3datr0n

to answer your query @wesakab Meta mask is going to be a bridge for DEX in future .. Basically it stores your private keys for any ETH address example my ether wallet and then without exposing your keys again and again .. Meta mask sings transaction on your behalf ..

Looks somehow like below on any DEX .. in below screenshot I have showen example of EtherDelta.

Hope this answers your query !