Slide Jumping, also called Coyote Jumping, is a technique that allows Samus to gain extra distance by jumping after sliding off a ledge. By waiting to jump until Samus is fully in the air after sliding, Samus can jump, accessing higher wall jumps and new ledges she normally wouldn't be able to, without the need for techniques like Infinite Bomb Jump, or Single Wall Jump.
This is useful in many areas of the game for different reasons, and uses inputs similar to Slide Jump Pseudowaves.
"Roll jumps" were popularized by Donkey Kong Country on the SNES. Performing an action while walking off a ledge or in mid-air can sometimes increase the window of a time a player has to jump, even when there's nothing to jump from, allowing a player to jump while mid-air. "Hangtime" properties like thse can be exploited to increase your jump distance or give you extra height, such as unmorph jumping in the original NES Metroid. In Metroid Dread, sliding off a ledge will increase Samus's travel distance while still letting her jump for a short period of time.
Officially, Nintendo refers to the technique as a "Slide Jump." The name "Coyote Jump" comes from the titular "Coyote Time," an action epitomized in Looney Tunes by Wile E. Coyote, who would frequently walk off cliffs, find himself hanging in mid-air, and then scramble his way back to the ledge before gravity kicked-in a few moments later.
Other names for it include "DK jump" or "Diddy jump," named after the characters in Donkey Kong Country.
Maintain your height and get a slight boost of speed, but no jump after.
Different than a slide jump, performing a Dash Melee (running, then performing a melee attack) off a ledge will increase Samus' travel distance slightly, but you can't jump after without Spin Boost or Space Jump.
Examples of Slide Jump include Early Bombs and Early Grapple Beam.
Position Samus near a ledge.
Slide off the ledge, then press jump after you start to fall.
If done correctly, Samus will still be able to jump.
In Dairon, below where you collect Wide Beam. Start by standing to the left of the morph ball tunnel leading to the lava (tomato soup).
Slide through the tunnel, jumping once you reach the other side. Hold left toward the wall you just passed, then wall jump off it and catch the ledge above and to your right. Morph into the morph ball tunnel.
On the other side of the morph ball tunnel, unmorph, and face right. Slide through the morph ball tunnel, and jump right as Samus begins to reach the center of the gap between the two ledges. If done correctly, you should be able to reach and grab the ledge on your right, across the small gap there.
If you fail the jump for any reason, try and land on the sloped platform on your right, then quickly jump off the slope to try and grab the ledge on the left you slid off from. Sometimes the Ply (flier) enemies will interfere, sometimes beneficially with a damage boost to help you to either ledge, and other times sending you straight to the tomato soup, forcing a reset to checkpoint.