There is an introductory article to the series found here.
What does it mean to be LIGHT?
Thematically light monsters are caring, protective, and strict. In a lot of themes they are put up as a counterpart of the dark attribute which can occasionally confuse the identity. But generally the light represents the protection of others. That can come in the form of sacrifice or helping one another. Light monsters can channel powers of the divine and send their enemies away from this world to never return. Where the light shines brightest great things can happen. We see this with cards like the Lightray series of monsters that count light monsters for their summoning conditions. Do not take this to mean that the light only represents good though. In the Duel Terminal storyline both Worms and Fableds are villains who primarily belong to the light attribute.
Healing
I can neither confirm nor deny I used this example to upset Duel Links players
One of the clearest early themes for light monsters was healing. Cards like the Immortal of Thunder and Hysteric Fairy give you boost to life points at a huge cost. Then there are cards such as Absorbing Kid from the Sky and Radiant Jeral that have conditional life point gains with reduced stats. As I'm sure most of you can tell, these cards are not good. Some would even say they're garbage. Some would say they are so bad you have to throw them in a separate bin from the garbage. However, it is not only these cards that have heavy downsides to the healing that are bad. Any card entirely dedicated to healing is pretty much doomed to fail.
Even cards that are playable by virtue of having some other effect, such as Wiz, Sage Fur Hire, will show how irrelevant healing effects tend to be. Even if the heal gets you out of OTK range, you still need to re-establish your board in order for the heal to matter. As such, healing is generally obsolete and has been for a long time. This is of course also rather obvious with how many decks choose to play Upstart Goblin despite the drawback. Affecting the boardstate is generally more powerful than affecting your life total.
Banishing
While banishing as a mechanic is far from unique for the light attribute, it is certainly most prevalent here. Other than being one half of the chaos series of cards, they have a wide swath of cards that manipulate the banish pile. There are cards such as Lightray Grepher that let you set up the cards you want to banish. Cards such as Eclipse Wyvern reward you for banishing it. Lastly, we have a couple cards that banish all cards such as Banisher of the Light and Banisher of the Radiance.
That one guy at a party that just will not stop talking about banishing
There are multiple archetypes in the light attribute with varying degrees of this banish theme. Some examples are ABC Unions, Cyber Dragons, PSY-Frames, Kozmos and a fair few more. Some of these use it as an abstract way to represent a mechanic like with ABC Unions and Kozmos tagging in and out. Other decks have multiple pieces of banishing removal or use banishing as a resource. But the big one I haven't mentioned yet is Metaphys. Metaphys as an archetype is all banishing all the time. Just look at Metaphys Daedalus, a card which does nothing but banish. When banished, banish a card that has an effect when banished. When special summoned, banish them all.
Regardless of what being banished represents flavorwise it is all across the light attribute.
Gathering
When light monsters come together they can accomplish great things. Lots of light monsters have effects or conditions based on having other light or archetypal monsters in your resource pool. There's the entire series of Lightray monsters, which have sadly not seen much play in serious decks outside a couple niche strategies. A more famous example of a monster that synergizes with other Light monsters is probably Judgment Dragon, the boss monster of the fan favorite Lightsworn archetype. This card does not just enforce having a lot of Lightsworn monsters in the grave, but instead a lot of Lightsworn names. This is probably the strongest representation of this mechanic across all of Yugioh, as it really is all the Lightsworns coming together to summon one of the strongest bosses of their time.
Closing Thoughts
The light attribute does a lot of different things, but it still retains some identity. What I would want in the future is for Konami to keep using the banishing mechanic in creative ways as well as rework or expand on the other themes. The gathering mechanic generally fits worse in the modern speed of the game, with the conditions either being too easy to meet turn 1 or too slow. Healing has the issues I discussed in that segment as well as being a bit boring. Reworking the healing to be more about health and healing matters style mechanics, such as the Aromage archetype, might be a good direction to go with it. Like I said, if the healing has no board impact it will very often do nothing for you. Let us hope for a bright future.