Can trades through MetaTrader4 be automated?

Earlier Zerodha had introduced Pi-bridge for algo trading through Amibroker.
Data vendors like GDFL also provide Nest bridge support.

If I were to use MetaTrader, will it be possible to automate trades completely, or will I only get signals based on strategy but will have to execute orders manually. If so, what would I need to make it completely automated.

You cannot automate trades without taking approvals from the exchanges. I’d suggest you speak to my colleague Siva - [email protected] regarding exchange approvals.