In MetaTrader terminals, the minimum trade amount is determined by the margin required to open a trade. It depends on the following factors:
The trading instrument
The lot size
The current price of the asset
The margin requirements set for the instrument
What is the minimum amount required to open a trade?
For several instruments, the lowest margin requirement is just $1 USD. For example, to open a trade for instruments such as EUR/USD, GBP/USD, AUD/USD, or NZD/USD, only $1 USD in margin is required. You can read about how margin is calculated in this article.
You can also check the minimum trading amounts for each instrument on the Instrument Specifications page.
Please note that the company reserves the right to change trading conditions (including the minimum trade amount) at any time and at its sole discretion.