What is happening
The profit MetaTrader shows on an open trade is the raw price move. Your actual result also includes costs: the spread you paid to enter, any commission, and swap (overnight financing) if you held the trade past the daily rollover. Once those are counted, a small 'profit' can turn into a small loss.
The three costs, explained
The spread is the gap between buy and sell price — you start slightly behind by exactly that amount. Commission is a per-lot fee some accounts charge instead of a wider spread. Swap is a daily credit or debit for holding a leveraged position overnight, based on interest rate differences; it is often a cost, and it can be large on some instruments.
Hold a position for several nights and swap can quietly eat a meaningful chunk of your gain.
How to see it clearly
In the trade tab, add the 'Commission' and 'Swap' columns so you can watch them accrue. In your account history, the profit shown for a closed trade already nets these off — compare it with the raw price move to see the true cost.
How to prevent surprises
Check a symbol's swap rates before holding overnight, especially over a weekend (many brokers charge three days of swap on one day). Factor spread and commission into whether a trade is worth taking. For short-term trading, costs matter more than beginners expect.
Broker's fault or yours?
These are disclosed costs, not tricks — the responsibility is to understand them before trading. That said, unusually high spreads, commissions, or swaps are a fair reason to compare brokers, since costs directly shrink your results.