Melee Counter

The Melee Counter is a new technique in Metroid: Samus Returns. When a charging enemy is about to attack Samus, she can parry the attack and then follow up with Beam or Missile shots, or a Lethal Strike or Overblast. A successful Melee Counter will also fill up Samus's Charge Gauge. The Melee Counter can even be used against Metroids, leaving their weak points vulnerable to attack and making them easier to battle than they were in Metroid II: Return of Samus. The Melee Counter also means that Samus no longer has to dodge attacks from advancing enemies, which she did have to in previous games.

E3 website
"Classic Metroid II: Return of Samus gameplay is joined by a wealth of new content, including a set of brand new abilities that utilizes a mysterious energy resource called “Aeion,” a powerful melee counterattack, and 360-degree Free Aim Mode."

On-screen tutorials

 * "Use your Melee Counter right before a charging enemy makes contact to parry. After doing so, you will automatically take aim. Press [X] to use your Melee Counter now."
 * "Press [X] to use your Melee Counter right before a charging enemy makes contact."