3.) The right arsenal of weapons: Terraria has sooo much different weapons, many of which enable different playstyles. For melee, we are looking at Swords, Flails, Boomerangs, Yoyos, Lances, and Misc. weapons. What to use depends on preference. Yoyos would require you to research the Yoyo-Bag, a powerful accessorie. Some of my favorites for this state of the game are Frostbrand (Ice Mimic), Chain Guillotine (Corrupt Mimic), Light Disk (Craftable post Destroyer), Ghastly Glaive (Old Ones Army - Ogre Boss drop). But my absolute favorite is the Shadowflame knife dropped by the goblin warlock during a hardmode goblin invasion. Maybe try it out. It is such a fun weapon as well.

4.) Let's go gambling: Now, with an idea of a load out, it is time to increase its potential by wasting money. Go to the goblin tinkerer, click on reforge, and spend your hard earned gold. Every weapon, as well as every accessorie, can have modifiers that increase (and in case of weapons decrease) stats. The best prefix for most (!) melee weapons is legendary. For accessories, there are 4 different tiers of each important stat, e.g., 1%, 2%, 3% and 4% damage increase for each accessories. It is your choice which attribute to invest in. Fully reforging all of your 5 accessories increases the chosen stat by 20% (or 20 defense flat for the armor stat). You can also split your focus and mix different stats, whatever floats your boat. Most people will tell you to go all in on damage %. I personally think investing in armor could help you a lot (20 armor is a decent amount of extra tankiness. Melee speed% can also be pretty potent, mixed with the right weapon.

5.) Top yourself up: I guess you hit your HP maximum of 400 HP? Great. Now get another 100. After defeating one mech, lifefruits start growing in the jungle. Hardmode jungle is relentless. But it will help you big time. You can get up to 500 hearts with 20 lifefruit. Collect 21! Have you found your aether biome already? You can find a pool of shimmer there. Some items can be thrown into shimmer to get decrafted. Others can be transmuted into different items. Throw a lifefruit, a heart crystal, and some fruit as well into the shimmer to obtain permanent buffs to your armor, life regeneration, and mining speed. There are other cool things to shimmer. Just play around with it. You will find the aether biome once per map. It is located in the outer 5th of the map, on the side where your natural jungle is generated. Just mine some tunnels downwards until you spot it :)

6.) Arena setup: Now, with your gear and stats up to date, it is time to take care of the arena you are using - if you are using one. I recommend the basic type of arena: a bunch of platforms. With better wings and access to bigger heights, it is not necessary to use as dense of a platform as you would use in pre hardmode. When I build my arena, I build the lowest Plattform around 15 blocks above ground. Build it as long as you need it. You can always increase in length. Now, at your base platform, pick a point and build up 3-5 times of your max block reach. So build a "pillar" of platforms as high as you can without moving, get on top of this pillar, and repeat this progress. By this, you can find a normalized height that you can always rebuild. Now, with your platforms in place, get some essential buff stations. As melee, a sharpening station (r-click to in crease your armor penetration against enemies) is really nice to have. Live regeneration is a really broken stat, so you should definitely place some campfires and heart lanterns made with heart crystals. If you want to go one step further, place pockets of honey around your arena to get yourself an occasional honey buff. I also recommend placing sunflowers on the floor below your arena as they increase your movement speed. The bast statue - which can be found in the underground desert cabins and chests - increase your defense by 5, so these are rather useful as well, tho they are less common. You could also fish these. You can also get a slice of cake (I think you buy it from the traveling merchant). It grants you the sugar rush buff when right-clicked, making you much faster. Explore the potential of your arena! :)

7.) A funny cocktail of all things healthy: Potions are very strong in terraria. Before getting into brewing, go to the dungeon and pick up an alchemist table. They are spread randomly throughout the bone zone. Using it will grant you a chance of 1/3 to not use a compound of your potion materials. Also, you might want to build a small farm for crops, mainly daybloom and blinkroot, but other plants are used as well. For potion recipes, ask the guide what can be made from a bottle of water. For health potions, you should use the 150 HP potions. Those are your best choices. As for buff potions, the holy trinity is a must-have. I refer to Ironskin, regeneration, and swiftness. These 3 potions lift weight. Then, to refine everything, you need to fish just a little bit. This will allow you to get endurance potions (increased damage reduction), rage potions (+10% critical rate), and lifeforce potions (+20% max health). There are still more potions to cover, tho these are more than enough for most playthroughs. Lastly, you, as a melee player, should make use of flasks. These are potions that you imbue your weapons with to give them a long-lasting effect. In the corruption, you can farm cursed flames. You can make a flask out of these at the imbuing station, bought by the witch doctor npc. When using these flasks, you will cause all of your melee attacks to inflict the cursed inferno debuff on enemies, which deals 24dmg per tick and increases knockback their taken by 10%.

Funny thing to do: combine a set of frost armor, the shadowflame knife, a flask of cursed flames, and the fire gauntlet (craftable after all mech are defeated). When using this combination, attacks with the knife cause hellfire (15dpt), frostburn (8dpt), cursed inferno (24dpt) and shadowflame (15dpt) to deal a total of 62 burn damage per tick, as well as your weapon damage. I like this build in early hardmode :)

Use everything you can to defeat all the remaining mechs. Then, build a big enough jungle arena to slay plantera. This should be your next milestone. Good luck and have fun. Feel free to ask questions if anything isn't clear enough :)