There are three main reasons for the automatic closing of a trade in MetaTrader terminals:
A Stop-Out was triggered on your account
A Stop-Out operation means that your positions were closed forcibly at the actual prices at the time of closing. This happens due to reaching the allowable level of losses and the resulting lack of funds to further maintain open positions.
Closing of trades by the Stop-Out procedure occurs when the ratio Equity / Margin reaches 50%.
In the MetaTrader terminal, the level of funds (margin level) is displayed in the "Trade" tab when there are open trades as the indicator "Level". It is determined by the formula: Level=(Equity/Margin)×100%
In the account history, a Stop-Out operation will have a comment like [stopout] or [so].
An Expert Advisor or robot is enabled in your trading terminal
Expert Advisor / Robot / Auto-trading is a certain automation setting, which, when enabled, independently opens and closes trades according to the given algorithm.
As a rule, the presence of an enabled Expert Advisor is displayed in the form of a "smiley face" in the upper right corner of the chart.
If the smiley is sad – auto-trading is not enabled.
If the smiley is smiling – it means your Expert Advisor is allowed to trade, so it will open and close trades independently.
The Expert Advisor leaves marks indicating its activity. In the Account History, in the "Comment" column, the Expert Advisor may leave a message that this trade was opened/closed by the Expert Advisor. At the same time, some Expert Advisors do not leave marks depending on their internal settings.
It is important to make sure that the trades were not completed by the Expert Advisor by checking the account history, and check if it is enabled in the terminal.
In the case of set profit or loss limits (Stop-Loss or Take-Profit)
When opening a trade in the MetaTrader terminal, you may be offered to set profit and loss limits. In case you set such limits, then upon reaching these conditions, the trade will close automatically. Profit and loss limits can be set both when opening trades and for currently open trades.