No, you cannot login to MetaTrader5 if your trading account is opened for MetaTrader4.

Unfortunately, there is no trading account which is compatible with both MetaTrader4 and MetaTrader5 at the same time.

In case your Forex broker offers both MT4 and MT5 trading platforms.

You may need to open trading accounts respectively, so you can use both trading platforms but with different trading accounts.

For MT4 and MT5 trading platforms, different servers and different account numbers will be provided.

For your information, both FBS and FXPro offers MT4 and MT5 trading platforms together.

With these brokers, you can open several trading accounts for MT4 and MT5 managed under the same client portal.

List of Forex Brokers