Our margin rules are:

Margin Call: 100%

Stop Out level: 70%

If you reach 100% Margin:

You will not be able to open any more trades. 

If you reach 70% Margin or below:

A "Stop Out" will occur at which MetaTrader will start to close your open positions one by one.

You may either raise your total equity by adding more margin to your account or decrease the margin you're trading on by shrinking the lot size of your holdings to maintain your margin levels higher.