MetaTrader is just a platform which ease the process of trading for you. It is provided by the vast majority of brokers, I guess almost all brokers offer the access to trading via MT4 and MT5. So, it's kinda incorrect to claim that all the brokers are scam, then according to your question there is no trading at all, because almost every broker prefers MT4 as the main trading platform. The rest part of brokers offers their own trading platforms which were created specially for traders. In my opinion, scams brokers can be revealed in other way. For example the lack of regulations, certifications and licenses can tell you about the reliability of a certain broker.
You need to check on brokers for regulations, account type, any potential red flags cause MT4 itself is just a trading platform. There are still trustworthy broker that use MT4.
There have always been normal and reliable brokers on Forex, and there were also scammers. Therefore, I was looking for a broker with a positive reputation, which has been working on the market for a long time, which provides minimal spreads, instant execution and timely withdrawal of profits. I first tested the trading conditions on small accounts and chose fxopen for trading.