Meta Knight's range stinks. If you constantly move while using your lagless projectile techs like short hop Header and Sun salutation landings, you can actually evade most of his moves and punish him on reaction. Specifically, landing during the charge animation of Sun Salutation gives you the ability to either grab, shield jump, side step, or block in addition to just shooting it. When combined with turnarounds, this can really frustrate Meta Knight's approaches. Staying at a distance also gives you an opportunity to avoid and punish his B moves. Offstage, you can use your superior air mobility to maneuver around his Nair and back air. If you stay near the ledge for a moment, you can condition them to try to stage spike you, which you can then avoid and punish by hovering above or below the ledge. I usually hover below and then Up B or Header. Header can spike his Up B with proper timing, and you can bait this by forcing him to use his jumps offstage. Despite his size, Meta Knight is still easily comboed. Just create openings with your projectiles and go to town.
If they try to adapt by jumping over your projectiles, you can either use your Header Feint Ftilt or set up a Fair-Salutation wall. The salutation covers the ground, and while it's moving, you run forwards and do a retreating Fair so you end up back where you started. This can be combined with landing while charging your Sun Salutation to mix up your wall's options. Remember, every fully charged Salutation heals you for 2% regardless of whether he shields or not, so you can actually use this time to heal through Meta Knight's combo damage.
If you feel pressured or he tries to combo you, just DI offstage while timing your air dodges. Meta Knight wants you close to him in the air so he can Up B you, so make him work for it. Plus, if he follows you offstage, he wastes more jumps, which can lead to easy spikes (this works for most multi jump characters like Pit, Kirby, Charizard, etc. plus Yoshi).
