A metro: frequent underground train found in built-up areas with high populations. Generally depicted as a forward-facing train traveling along tracks or rails and emerging from a tunnel. Color varies by platform, but most designs feature red-accented trains.

Apple's artwork shows the characters IL2 which may refer to one of the more locked-down buildings at Apple's Infinite Loop Headquarters during iPhone development (IL2 = Infinite Loop 2). WhatsApp includes an “M” transit-style logo, like the Ⓜ️ Circled M emoji, as well as an “F” route marker. JoyPixels displays “JOY” above the windshield.

Apple previously depicted this emoji as a white train outline overlaid on a blue square background. Samsung's initial design did not feature a tunnel.

This emoji predates the inclusion of emojis within Unicode. It was first added to early Japanese emoji keyboards by Softbank in 2000.

Metro was approved as part of Unicode 6.0 in 2010 and added to Emoji 1.0 in 2015.