Pros: Marth has amazing set ups and combos.
His grabs are one of the best in the game. (The range is crazy) His up throw is one of the best way to get a combo started and to land a kill. You can up throw chain grab Fox and Falco at low percents and start to up tilt them at around 30%. Down throw, forward throw, and back throw are good for edge guarding. Speaking of edge guarding, that is one of the many things Marth is very good at. If you knock your opponent of the map, it is always a good idea for a Marth player to try to go out and back air or down air the opponent. *NOTE Only do this if you are certain the opponent will comeback. If they probably can't, it is probably a good idea to ledge hog. Another thing you have to master in order to play Marth is you have to know how to use his sword. The tip of sword does the most damage and it has a meteor affect when using his down air. This is when the forward smash comes into play. If you get the tipper on the forward smash, it deals massive damage. This a great way to get an edge guard opportunity. Marth's tilts are also very good. His up tilt gets combo's started. His down tilt is a great way to edge guard and to lead into a grab or forward smash. His forward tilt has a lot of range and can be used to trick your opponent. His special attacks are used mainly for edge guarding. His neutral B is called Shield Breaker. Its good to use in the air (Mainly against fox and falco). Counter is also a good option at the ledge for edge guarding. His recovery is very good and can be used as a kill move if the move is reversed. Dancing blade (side special) has many options. It's good to combo with and for edge guarding.
Cons: Marth can easily be camped by projectiles. He is also a fairly easy character to combo.
I feel like Marth's worst match ups are Sheik and Jigglypuff. (I'm not sure about Ice Climbers) These characters are really good at camping Marth. Marth can't really take any needles or lasers from Sheik or Falco (Especially on FD). Jigglypuff is already a campy character and Marth has a really hard time trying to get things started with her. Fox and Falco can also easily combo Marth.
That's all I have for right now. Thanks for reading my first guide! I just wanted to try writing one and see how it would go.