On 18 June 2026, $8.3 trillion in options notional expired. SPY had a max pain level of $725. The market closed at $746. That is a $21 gap above the gravitational field dealers had been managing all week.

VIX dropped 9.3% on the day. The put-to-call ratio swung from 1.123 to 0.889 inside a single session. Every major symbol in the universe was sitting in negative gamma territory. And yet, most traders either had no idea what was happening mechanically, or they were waiting to read someone else’s interpretation of it afterwards.

This piece changes that. We are going to explain exactly how gamma works, why it behaves differently across each expiration type, and what Thursday’s reversal and the June quarterly close tell us about how markets function when options positioning reaches extremes.

This is not a textbook lesson. Think of it as the conversation you would have with someone who actually trades this stuff, over a pint, before the next session opens.

1. What Gamma Actually Is

Start here: an option’s delta tells you how much the option moves for every $1 move in the underlying. If SPY rises $1 and your call’s delta is 0.50, your call gains $0.50. Simple enough.

Gamma is the rate at which that delta changes. It is the speed of the speedometer, not the speed itself. When gamma is high, a small move in the underlying causes a large and rapid shift in delta. When gamma is low, delta drifts slowly and predictably.

Here is why that matters for the market as a whole: options dealers (the banks and market makers who write most contracts) are not directional traders. They hedge their books constantly, trying to stay delta-neutral. Every time SPY moves, they have to buy or sell the underlying to bring their book back into balance. When gamma is high, those hedging trades become large and frequent. When gamma is elevated across the entire market simultaneously, those hedging flows are large enough to physically move price.

So gamma is not just a Greek on your broker platform. It is a structural force that shapes intraday price behaviour, sometimes more powerfully than any news event.

2. How Gamma Stacks Across Expiration Types

Not all options expirations are equal. The gamma profile, the market impact, and the trading opportunity differ dramatically depending on whether you are dealing with a same-day expiry or a two-year LEAP. Here is how each one works:

0DTE: The Gamma Volcano

Options expiring the same day they are traded have almost infinite gamma at the money. Think about it mathematically: an at-the-money option one hour from expiry is nearly a binary bet. Either it finishes in the money or it does not. Delta can swing from 0.20 to 0.80 in minutes. Dealers have to hedge those swings in real time, which is why you often see SPX oscillating wildly around major round numbers intraday. Those round numbers are frequently max gamma strikes, and the dealer flow around them creates the choppiness you see on a 1-minute chart.

0DTE now accounts for roughly 45% of all SPX options volume on active trading days. That is a structural shift that happened over the past three years. The intraday pinning behaviour you see around 4,500, 5,000, or 5,500 in the S&P is not random. It is mechanical.

Weekly Options: Event-Driven Gamma

Weeklies carry meaningful gamma by Thursday or Friday before expiry, especially around earnings and macro events. Institutional desks routinely hedge event risk through weekly options, which is why you often see large gamma concentrations at clean round-number strikes in the week leading up to a Fed decision or CPI print. When the event resolves, that gamma collapses and the associated hedging flows disappear, sometimes producing a sharp directional move even when the news itself was benign. That is the “sell the news” dynamic in mechanical terms.

Monthly OpEx: The Classic Pin

The third Friday of each month is the most-watched expiry for a reason. This is where most retail and mid-size institutional options settle. Gamma builds across the prior two weeks, and as expiry approaches, price tends to gravitate towards the strike with the greatest concentration of open interest. That gravitational pull is not a mystery or a conspiracy. It is a mechanical consequence of dealer hedging. The closer a strike is to being at-the-money at expiry, the more frantic the hedging becomes. As multiple strikes compete, the market gravitates towards the one that minimises the aggregate payout to option buyers. That is max pain, and we will explain it fully in the next section.

Quarterly OpEx: When Everything Expires at Once

Triple witching occurs when stock index futures, stock index options, and stock options all expire on the same day, which happens four times per year. In June 2026, this coincided with broader quarterly positioning rolls, putting total notional at approximately $8.3 trillion. That figure is not just a big number for headlines. It represents a structural reset of the entire options market. All of the gamma that had been accumulating over weeks gets settled simultaneously, and the hedging flows that underpinned the previous price regime are suddenly gone. This is why markets often behave erratically in the session immediately following a quarterly expiry: the gravitational field has been switched off, and positioning is starting from scratch.

LEAPS: The Slow Anchor

Long-dated options (one to two years out) carry very little gamma precisely because there is so much time for the underlying to reach any given strike. The option does not need to be actively hedged in the way that a short-dated option does. However, LEAPS carry enormous vega, meaning they are highly sensitive to changes in implied volatility. When VIX spikes, LEAPS holders can see significant mark-to-market losses even if the underlying has barely moved. This matters for understanding why a sudden volatility event like a Middle East escalation can damage portfolios that appear to have no short-dated exposure.

3. How Dealers Hedge Gamma (The Magnet Mechanism)

Understanding the magnet effect requires understanding one core rule of how dealers operate: they aim to be delta-neutral at all times. They do not want directional exposure. They want to earn the spread and collect premium. To stay neutral, they must continuously adjust their position in the underlying as price moves.

Here is how that creates the magnet:

This process is the magnet. It is not manipulation. It is a predictable mechanical consequence of how dealers manage their books under standard financial practice.

4. Why Max Pain Works: The Mechanics

Max pain is the price at which the total value of expiring options (across all strikes, both calls and puts) is at its lowest. It is the price that causes option buyers the maximum collective loss. The concept sounds cynical, but the mechanics behind it are simple and structural.

As expiry approaches, dealers are running their largest gamma exposures near the money. At any given moment, large blocks of open interest are sitting at nearby strikes. The natural flow of dealer hedging happens to be self-reinforcing in the direction of max pain: buying near call walls and selling near put walls stabilises price in the zone where options expire worthless.

Max pain does not work every time. It works most of the time when there is no dominant exogenous catalyst. Think of it as one of several forces acting on price simultaneously. On a quiet OpEx Friday, it can dominate. On a day when $8.3 trillion in notional expires alongside a geopolitical resolution and a 9.3% VIX collapse, it gets overridden.

The value of tracking max pain is not in predicting the close to the dollar. It is in understanding where the gravitational baseline is, so you know how hard an exogenous force would need to push to break from it. Our Options Calendar tracks this in real time across all major instruments.

5. Negative vs Positive GEX: When Gamma Amplifies vs Dampens

Gamma Exposure (GEX) measures the net gamma position that dealers are running across the market. The sign matters enormously.

On June 17 (the Thursday before quarterly close), every major symbol in the tracked universe was registering negative GEX. That is a universal market-wide condition, not a single-name quirk. When the entire market is in negative GEX simultaneously, any catalyst, positive or negative, will be amplified. The reversal that occurred that Thursday was not just a “bounce.” Dealer gamma flows were actively pouring fuel on it. Negative GEX was the accelerant, the geopolitical update was the spark.

The P/C ratio flip from 1.123 to 0.889 in a single session is additional confirmation. A ratio above 1.0 signals put-dominant positioning (hedged or bearish). A ratio below 1.0 signals call-dominant positioning (unhedged or bullish). Moving from one to the other in 24 hours means institutions were rapidly unwinding protection. Combined with negative GEX, that unwind was not orderly. It accelerated the move.

6. What the June 18 Quarterly Actually Showed Us

Let us pull the threads together using the real data from this expiry cycle.

This is what our Options Intelligence page tracks across every expiry cycle: not just what happened, but what the gamma structure was telling us before it happened. The P/C flip, the GEX regime, the distance from max pain. Each is a layer of the same picture.

7. Hormuz, Monday, and a Freshly Cleared Gamma Slate

Here is the setup that matters most for the week ahead.

The quarterly expiry cleared $8.3 trillion in notional on Friday. That means the gamma structures, the dealer hedging flows, the max pain anchors, and the GEX regimes that governed price action all week are gone. The market begins Monday essentially from a blank slate in terms of options positioning. New contracts will be written over the coming days, but the density of open interest that existed last week has been reset.

At the same time, the Strait of Hormuz situation remains unresolved at a structural level. Whatever the specific update was that triggered Thursday’s reversal, the broader geopolitical risk is still present in the background. When a fresh geopolitical shock hits a market with thin options positioning, the effect is almost always amplified. There is no existing gamma structure to dampen moves, and any new positioning happens in a market that is still assessing risk.

The honest assessment is that Monday opens with elevated uncertainty not because of anything fundamental, but because of the structural vacuum that follows a quarterly expiry. That vacuum, combined with an unresolved geopolitical variable, creates the conditions for an outsized move in either direction.

8. How to Use Gamma Information: When It is Your Friend vs Your Enemy

Knowing gamma structure is only useful if it changes how you approach the session. Here is the practical framework:

The Two Questions That Frame Every Session

Both data points are available on our Options Intelligence page before the open, every session.

The One-Paragraph Version

Gamma is the engine underneath market magnetism. Dealers hedge it mechanically. That hedging creates gravity around max pain strikes, dampens ranges in positive GEX regimes, and amplifies moves in negative GEX regimes. Different expiration types carry different gamma intensity. 0DTE is a volt spike, LEAPS is a long, slow current. Quarterly expires flush everything and leave a structural vacuum. June 18 gave us all of these dynamics in one session: $8.3 trillion expired, SPY closed $21 above max pain as geopolitical relief overwhelmed the gravitational pull, the P/C ratio flipped, VIX collapsed, and now we enter Monday with thin options positioning, an unresolved geopolitical backdrop, and no established gamma anchor. That is not a reason to panic. It is a reason to adjust your expectations for range and be selective about when you trade.

Track the real-time gamma structure, GEX readings, and max pain levels across all 42 major instruments on our Options Calendar and Options Intelligence pages. Updated before every session.