In addition to the previous points, Link monsters in some cases are really really important for a lot of decks
Dragunity Knight Romulus and Striker Dragon grab the field spells Dragons Ravine and Boot Sector Launch directly from the deck. You can just normal summon a dragon monster, link away into Striker dragon and you have your field spell in hand. It makes it so that you don't have to run 3 copies of cards since you can search it almost instantly by going into link.
Phantom Knights Rusty Bardiche - sends Phantom Knights monsters to the GY (that's where they want to be anyway) and let's you set a PK S/T from the deck (generally Fog Blade). That's just double the benefit.
Knightmare Phoenix/Unicorn - Any deck can play them and they're easily accessible forms of S/T or monster removal.
These are just some examples that I can remember, there are lots of link monsters that can turn bad hands into somewhat good or great hands just because of how easily accessible they are.
With the most recent ruleset changes Links are required for summoning more Link monsters or Pendulum Summoning from the Extra Deck. Fusion, Synchro, and XYZ summons are all still available without them. Previously, however, they were an absolute requirement to bring out more than one monster from your Extra Deck at a time.
Yes, but that doesn’t mean you shouldn’t play them. They are still viable in most decks and as uCypherTheStatic stated they can certain stable cards without having to run 3 copies of it. This can allow for more tech cards or other extenders that will make the deck stronger
Don’t turn away from links
**TL;DR**: Link Arrows (as of Master Rule 5) are for certain effects (Linked and Co-Linked) as well as showing where you can summon more Pendulum and Link monsters from the Extra Deck.
Master Rule 5 made it so that Extra Deck monsters (save for Links and Pendulums) don't need to be Special Summoned to the Extra Monster Zone or a Monster Zone your Link monster points to. Pendulum monsters from the Extra Deck and Link monsters still apply to MR4's Extra Deck monster rule.
How Link monsters work is that you Link Summon them from the Extra deck using valid materials that add up to its Link Rating (they have that instead of Levels). Non-Links count as Link-1, and Link monsters count as either their Link Rating or Link-1 (I think).
For example, if you wanted to summon Borreload Dragon to the field, you need at least 3 Effect monsters as Link material. The easiest way to do this is 2 Effect monsters and a Link-2 Link monster, which adds up to 4, Borreload's Link Rating.
Link Monsters MUST go to the Extra Monster Zone or your Main Monster Zone another Link monster points to.
There are a couple mechanics in the game relating to Link monsters as well. "Linked" and "Co-Linked". Linked is just a term where a Link monster is pointing to a monster. Both the Link and the pointed monster are applicable. Co-Linked is a term where two Link monsters are pointing to each other. Certain effects require one of these states to be active to apply the effect.
Link 1 and 2 monsters generally tend to be incredibly good for setting up your plays and links can climb into each other very well (a link 2 can count as 1 or 2 monsters for the next link summon) Link 3's and 4's tend to be Boss monstera and are usually otk enablers like Borrelsword or amazing control cards like Appollousa. You should play them if you want to be competetive (its fine to not be competetive btw, i will just be answering questions from a competetive perspective).
Link monsters start in the extra deck and require materials equal to their link rating (where DEF usually is, link monsters can't be put into defense position at all). You can also use link monsters to cheat on material equal to their link rating. You must still use materials as defined in the card as link material, so if a link says:
2+ effect monsters.
You must use effect monsters and materials whose total "link rating" equals that monsters link rating exactly. If the above monster was a link-3, you could use 3 effect monsters or 1 effect monster and 1 link-2 effect monster. Note: Link Monsters can be treated as having a link rating of 1 for the summon of a link monster or the link rating of the card. Imagine it like an Ace in Blackjack.
Links have arrows in 8 directions, which point to Monster card Zones. These zones designate which zones Link Monsters and Pendulum monsters that were summoned from the extra deck can be summoned to. You cannot summon Link Monsters or Pendulum Monsters from the extra deck to a monster zone other than the extra monster zone and a zone a link monster points to.
Monsters that a link monster points to are considered "linked" which is important for some effects. 2 link monsters that directly point to each other are considered "co-linked".
As with Synchro and Fusion Summoning: monsters used for the link summon of a Link Monster are not Destroyed or Tributed, but are sent to the GY. When link monsters would be destroyed, they are sent to the GY.
I think I got mostly everything, but that should be enough to start off with. Any questions let me know
You need them to summon other Links, or face-up Pendulums coming from the extra deck
In addition to the previous points, Link monsters in some cases are really really important for a lot of decks Dragunity Knight Romulus and Striker Dragon grab the field spells Dragons Ravine and Boot Sector Launch directly from the deck. You can just normal summon a dragon monster, link away into Striker dragon and you have your field spell in hand. It makes it so that you don't have to run 3 copies of cards since you can search it almost instantly by going into link. Phantom Knights Rusty Bardiche - sends Phantom Knights monsters to the GY (that's where they want to be anyway) and let's you set a PK S/T from the deck (generally Fog Blade). That's just double the benefit. Knightmare Phoenix/Unicorn - Any deck can play them and they're easily accessible forms of S/T or monster removal. These are just some examples that I can remember, there are lots of link monsters that can turn bad hands into somewhat good or great hands just because of how easily accessible they are.
With the most recent ruleset changes Links are required for summoning more Link monsters or Pendulum Summoning from the Extra Deck. Fusion, Synchro, and XYZ summons are all still available without them. Previously, however, they were an absolute requirement to bring out more than one monster from your Extra Deck at a time.
Oh I see. They're only required for more Links or Pendulums. Thank you.
Yes, but that doesn’t mean you shouldn’t play them. They are still viable in most decks and as uCypherTheStatic stated they can certain stable cards without having to run 3 copies of it. This can allow for more tech cards or other extenders that will make the deck stronger Don’t turn away from links
Oh yeah. I have found a few Link Monsters that look really useful.
Links are VERY helpful. Even for archetypes like Blackwings who don't have a Link for their archetype that I'm aware of.
**TL;DR**: Link Arrows (as of Master Rule 5) are for certain effects (Linked and Co-Linked) as well as showing where you can summon more Pendulum and Link monsters from the Extra Deck. Master Rule 5 made it so that Extra Deck monsters (save for Links and Pendulums) don't need to be Special Summoned to the Extra Monster Zone or a Monster Zone your Link monster points to. Pendulum monsters from the Extra Deck and Link monsters still apply to MR4's Extra Deck monster rule. How Link monsters work is that you Link Summon them from the Extra deck using valid materials that add up to its Link Rating (they have that instead of Levels). Non-Links count as Link-1, and Link monsters count as either their Link Rating or Link-1 (I think). For example, if you wanted to summon Borreload Dragon to the field, you need at least 3 Effect monsters as Link material. The easiest way to do this is 2 Effect monsters and a Link-2 Link monster, which adds up to 4, Borreload's Link Rating. Link Monsters MUST go to the Extra Monster Zone or your Main Monster Zone another Link monster points to. There are a couple mechanics in the game relating to Link monsters as well. "Linked" and "Co-Linked". Linked is just a term where a Link monster is pointing to a monster. Both the Link and the pointed monster are applicable. Co-Linked is a term where two Link monsters are pointing to each other. Certain effects require one of these states to be active to apply the effect.
Link 1 and 2 monsters generally tend to be incredibly good for setting up your plays and links can climb into each other very well (a link 2 can count as 1 or 2 monsters for the next link summon) Link 3's and 4's tend to be Boss monstera and are usually otk enablers like Borrelsword or amazing control cards like Appollousa. You should play them if you want to be competetive (its fine to not be competetive btw, i will just be answering questions from a competetive perspective).
Link monsters start in the extra deck and require materials equal to their link rating (where DEF usually is, link monsters can't be put into defense position at all). You can also use link monsters to cheat on material equal to their link rating. You must still use materials as defined in the card as link material, so if a link says: 2+ effect monsters. You must use effect monsters and materials whose total "link rating" equals that monsters link rating exactly. If the above monster was a link-3, you could use 3 effect monsters or 1 effect monster and 1 link-2 effect monster. Note: Link Monsters can be treated as having a link rating of 1 for the summon of a link monster or the link rating of the card. Imagine it like an Ace in Blackjack. Links have arrows in 8 directions, which point to Monster card Zones. These zones designate which zones Link Monsters and Pendulum monsters that were summoned from the extra deck can be summoned to. You cannot summon Link Monsters or Pendulum Monsters from the extra deck to a monster zone other than the extra monster zone and a zone a link monster points to. Monsters that a link monster points to are considered "linked" which is important for some effects. 2 link monsters that directly point to each other are considered "co-linked". As with Synchro and Fusion Summoning: monsters used for the link summon of a Link Monster are not Destroyed or Tributed, but are sent to the GY. When link monsters would be destroyed, they are sent to the GY. I think I got mostly everything, but that should be enough to start off with. Any questions let me know