MT5 Expert Advisors

An Expert Advisor (EA) is a program that runs inside MetaTrader 5 and can analyse the market, open, manage and close trades automatically. EAs are written in MQL5, a language similar to C++. They range from simple helpers that manage your stops to fully automated systems.

What EAs are good for

• Trade management: moving stops to breakeven, trailing them, taking partial profits exactly as your plan says.
• Risk control: calculating position size from your stop, or closing everything at your daily loss limit.
• Fully mechanical strategies: rules precise enough to code completely.
• Testing: MT5's Strategy Tester runs an EA over historical data, including with real tick data.

The shape of an EA

Every EA is built around event functions. OnInit runs once at start-up, OnTick runs on every price update, and OnDeinit runs when the EA is removed. This skeleton shows the structure, including risk-based position sizing; the entry rule is left for you to write.

#include <Trade\Trade.mqh>

input double RiskPercent = 0.5;   // risk per trade, % of balance
input int    StopPoints  = 200;   // stop distance in points

CTrade trade;

int OnInit()
  {
   return(INIT_SUCCEEDED);        // runs once when the EA starts
  }

void OnTick()
  {
   // runs on every price update
   if(PositionsTotal() > 0)
      return;                      // one position at a time

   if(!EntrySignal())
      return;

   double ask  = SymbolInfoDouble(_Symbol, SYMBOL_ASK);
   double stop = ask - StopPoints * _Point;
   double lots = LotsForRisk(StopPoints);
   trade.Buy(lots, _Symbol, ask, stop, 0.0, "academy-example");
  }

bool EntrySignal()
  {
   // your rules go here, e.g. a sweep and a structure shift
   return(false);
  }

double LotsForRisk(int stopPoints)
  {
   double risk     = AccountInfoDouble(ACCOUNT_BALANCE) * RiskPercent / 100.0;
   double tickVal  = SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_VALUE);
   double tickSize = SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_SIZE);
   double perLot   = stopPoints * _Point / tickSize * tickVal;
   double step     = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_STEP);
   return(MathFloor(risk / perLot / step) * step);
  }

From code to live

1. Write and compile the EA in MetaEditor (press F4 in MT5).
2. Test it in the Strategy Tester on several years of data, including costs.
3. Run it on a demo account for weeks, comparing live behaviour with the test.
4. Go live on small size, ideally on a VPS (a remote server) so it runs when your computer is off.