What MetaTrader 4 is
MT4 is a broker-hosted trading platform: the broker runs the server, and the trader connects through a desktop client, the mobile apps or the browser-based web terminal. The platform handles charting, order entry, position management, and (via the Expert Advisor system) automated trading. It does not handle deposits, withdrawals, or KYC — those happen in the broker's separate web portal.
The platform was designed for forex trading as it existed in 2005: spot FX, CFDs on metals, and limited equity index exposure. It does not natively support stocks, futures, or options as exchange-cleared products. Every order passes through the broker's MT4 server, and the client's trade is with the broker. Whether the broker keeps the resulting risk on its own book, as a Market maker can, or passes it on to a liquidity provider with a back-to-back trade depends on the broker's execution model, not on the platform.
MT4 stays in use because of network effects: the library of Expert Advisors coded in MQL4, the third-party indicators and tools, and the trader familiarity built over two decades. Its successor MT5 has not displaced it.
How MT4 handles margin, pip values, and lot sizing
MT4 displays Margin, free margin, equity, and margin level in the Trade tab of the Terminal panel. The figures update in real time as positions move. Margin follows the margin calculation mode the broker sets in each symbol's specification (Forex, Contracts, Futures, Contracts Index or Contracts Leverage); on forex symbols it is driven by the contract size and the account's leverage.
Lot sizing on MT4 follows the standard forex convention on a symbol with a 100,000 contract size, the usual standard-account setting: 1.00 = 1 standard Lot size (100,000 units of base currency), 0.10 = mini lot (10,000 units), 0.01 = micro lot (1,000 units). The contract size is set by the broker per symbol and shown in the Specification window, so a mini-lot or cent-type account symbol can carry a smaller one. Most retail brokers configure MT4 to accept 0.01-lot increments; the symbol's specification shows the minimal volume and the volume step the broker has set.
Pip values are not displayed prominently in the standard MT4 interface. The trader either calculates pip value externally — pip × position size in base currency, converted to account currency — or uses a third-party indicator that computes it on the chart. MT4's symbol specification window (right-click the symbol in Market Watch → Specification) lists the contract size and the digits, from which pip value can be derived: on a 5-digit EUR/USD quote one pip is 0.0001, so pip value = 0.0001 × contract size, converted to the account currency.
Worked example: opening 1 standard lot of EUR/USD at 1.0850 in a USD-denominated MT4 account with 1:100 broker leverage holds $1,085 in margin (visible in the Trade tab). Pip value is $10 per pip — not displayed by MT4 directly, but inferable from contract specifications and lot size. A 50-pip move produces $500 P&L, displayed in the position's Profit column.
Placing, modifying, and closing orders
Order entry on MT4 happens through the New Order dialog (F9, or Tools → New Order). The dialog accepts: symbol (forex pair or CFD), volume (in lots), Stop-loss price, take-profit price, comment, and Order types type. The Type field shows the execution mode the broker set for that symbol (Instant Execution, Execution on Request or Market Execution); choosing Pending Order instead opens the four pending types: Buy Limit, Sell Limit, Buy Stop and Sell Stop.
Under Market Execution the broker sets the fill price without a further prompt, so the fill can differ from the quote on screen, and slippage during volatile conditions is part of that execution mode. Under Instant Execution the order carries the displayed price; if the broker does not accept it, a requote returns new prices. With a maximum deviation set, a new price within that distance fills without notice, and a larger move still produces a requote. Pending orders (limits and stops) submit a conditional order that activates when the market reaches the specified price. Stop-loss and take-profit can be set at order open or modified later via right-click on the open position.
Modifying an open position: right-click the position in the Trade tab → Modify or Delete Order. The dialog allows changing the stop-loss and take-profit levels. The position itself cannot be repriced (the entry is fixed at the historical fill).
Closing positions: right-click the position → Close Order. The dialog accepts a partial close (specify volume less than the open position). MT4 also supports Close-By: closing two opposing positions on the same symbol against each other.
One-Click Trading is a toggle on the Trade tab of MT4's Options window that removes the confirmation dialog from trade commands sent from the chart and the Terminal window, including closing positions and changing stop-loss and take-profit levels. Faster execution for active traders; higher chance of accidental orders for less-experienced users.
Broker variations on MT4
Although MT4 is the same platform, brokers configure many parameters that change the trader's experience. Lot minimums vary: 0.01 lots is standard, but some brokers raise the minimum to 0.10 lots on exotic instruments, and the Specification window shows the minimal volume and volume step for each symbol.
Spread structure differs by account type. Standard accounts typically carry no per-trade commission and build the broker's charge into a wider spread; raw-spread accounts quote a narrower spread and add a per-lot Commission. Both figures are set by the broker. With an assumed 1.2-pip standard spread against an assumed 0.2-pip raw spread plus $7 round-turn commission, one standard lot of EUR/USD costs $12 against $9.
Symbol naming conventions vary by broker. EUR/USD can appear as EURUSD, EURUSDm (mini-lot account), EURUSD.raw (raw-spread account), or EURUSD-MT4 — same underlying instrument, broker-specific suffixes. Expert Advisors that hard-code symbol names require adjustment to run at a broker with different suffixes.
Server time displayed on MT4 charts is broker-set. Many brokers set server time to GMT+2, moving to GMT+3 while US daylight saving time applies, so that server midnight falls at the 17:00 New York close. Trader confusion about session boundaries (London open, US open, market close) frequently traces back to server time vs local time mismatch.
Common mistakes on MT4
Volume field misread as units rather than lots: a trader who types 100 intending 100 units has entered an order for 100 lots, which on a symbol with a 100,000 contract size is 10 million units of base currency. The position notional on EUR/USD at 1.0850 would be $10,850,000, requiring $108,500 in margin at 1:100. If the account's free margin is below that, or 100 lots exceeds the symbol's maximal volume, the broker rejects the order; otherwise it fills at 100 lots. Volume = lots, not units. Always.
One-Click Trading switched on without noticing what it does: the first time it is enabled, MT4 shows its Terms and Conditions, and the trader must tick “I Accept these Terms and Conditions”, a step that can be clicked through without reading. Once it is on, a click on the buy or sell button of the chart's trading panel submits an immediate order with no confirmation, and closes and stop-level changes from the chart or the Terminal window also go through without a prompt. Leave One-Click Trading off until the order flow is familiar; it is switched on and off on the Trade tab of the Options window.
Stop-loss in pips vs price level: the New Order dialog accepts the stop-loss as a price level (e.g. 1.0820 for a long EUR/USD entered at 1.0850), not as a pip distance. Entering 30 in the stop-loss field is read as 30.0000. On a buy, a stop-loss must sit below the current Bid, so MT4 rejects that level; on a sell, 30.0000 is a valid stop so far above the price that it never triggers. Always enter the absolute price level.
EA failures during fast markets: Expert Advisors rely on tick-by-tick processing. During news releases when ticks arrive in bursts, an EA may miss tick events, fail to fire stop-loss adjustments, or place orders out of intended sequence. EAs designed for normal-volatility conditions often misbehave during the seconds around major data releases.
Demo vs live account confusion: running the same EA on a demo account first, then attaching it to a live account without realising the same EA is now placing real orders. MT4 can store logins for several trading accounts, and the open chart profile, with any EA attached to its charts, carries over when the trader switches account unless a profile named after the new account exists; whether that EA keeps trading depends on the “Disable Auto Trading when the account has been changed” option on the Expert Advisors tab of the Options window. The visual difference between demo and live charts is minimal. Always check which account is connected before enabling a new EA on live.