Fans with tickets to opening day at Nationals Park may want to arrive earlier than in past years to ensure that they’re in their seats for Max Scherzer’s first pitch, though being in the ballpark for Mets pitcher Bartolo Colon’s first at-bat could be the bigger treat.

The Nationals held a demonstration Monday of the new Major League Baseball-mandated metal detection screening procedures that all fans entering Nationals Park must pass through this season. The Nationals installed walk-through magnetometers, or metal detectors, at all gates except for the third base gate and the first base ADA gate. Fans entering through these two gates will be screened with hand wands.

“We obviously encourage everybody to come early to the games,” Nationals vice president of ballpark operations Frank Gambino said. “We realize that people in Washington, D.C. are probably familiar with metal detection. … Still, to get used to the process, please come early, take your time; there’s a lot different things to do here before the game starts.”

Upon arriving at the gate, fans will have their bags checked as in previous seasons. After placing items such as keys, cell phones and cameras in a provided basket, fans will proceed through the metal detector. If the metal detector does not alarm, fans will proceed to the turnstile to scan their tickets and enter the ballpark.

If the metal detector alarms, fans will be subject to a secondary screening with a handheld device before proceeding to the turnstile. The metal detectors are designed to indicate which part of the body — the upper, middle or lower torso — alarmed. A list of prohibited items is available on the Nationals site.

The screening program is part of MLB’s work with the Department of Homeland Security to elevate and standardize safety procedures throughout the league. It will be in effect at every ballpark except Wrigley Field, which is undergoing extensive renovations, by opening day.

Fans entering Nationals Park for the Winter Classic on Jan. 1 were subject to handheld metal detection. Gambino said the Nationals began installing the walk-through metal detectors after that game. The team hired additional security personnel and trained them on the screening procedures, which will be required for every event at Nationals Park beginning with an exhibition game against the Yankees on April 4.

The team will add more points of entry at some gates to make the transition to the new screening procedures as smooth as possible. There will be dedicated season ticket holder lanes at the right field, left field and home plate gates — a benefit the team introduced at the center field gate last season — beginning this year.  There will also be dedicated lanes for fans without bags and fans with medical conditions.

Asked about the cost of implementing the new screening program, Gambino would only say it was a “substantial investment.”