So Arne has brought up Melomels - using fruit & honey together. There's a few ways to make a melomel, and Arne suggested one way (that I do, more often than the other).
You can add both the honey and the fruit upfront. Most fruits SG naturally runs between 1.020 - 1.040, so this is in addition to the sugars provided by the honey. Most mead recipes call for 3lbs / gallon, but when you add fruit, it gets trickier due to the added sugars... So ya gotta measure, or end up with firewater.
Another way to make a melomel is to add the honey upfront, get the fermentation started and add the fruit to the carboy under airlock, when the SG gets < 1.020. When doing this, leave plenty of head space both for the incoming fruit and the froth created from adding additional sugars to a fermentation.
These two methods create two different drinks. When the fruit is added to a fermentation, the heat from fermenting and the activity of the yeast, change the flavors of the fruit in more of a Fruit Wine-style, whereas if you add the fruit post-primary fermentation, after a majority of the heat during fermentation has been created and dissipated, the yeast are past their most-active point and things are on the "backside slide" - this retains more of the original flavor from the fruit.
As well as tampering with your SG, adding fruit will mess with the TA/pH of the wine, and can require action to balance it - acidic fruit like elderberries or blackberries might call for reducing the acid while peaches or pears will have you adding additional tartaric acid.. When you "Nail it" on a batch, you'll cry if you didnt have measurements.
So thats a rough intro to Melomels.
Yeast-Derived additives; these are things like Booster Blanc/Rouge, Opti-White/-Red.. Added at different times (beginning or end of fermentation usually), they have different outcomes... Overall, they help to prop up the mid-palette in fruit wines, they also help to retain color, freshness/brightness, can increase mineral-type sensations on the palette, help to buffer against oxidation.. Lots of nifty things, but they contain small amounts of yeast nutrients so adding them too late (say bulk aging) isnt wise due to spoilage organisms being able to take advantage of those same nutrients.. Generally, added around yeast-pitch or when racking under airlock (somewhere between 1.010 - 1.020) is about how I do it.
Tannins have came a long way in the last few years, and while I brought them up - they're a subjective thing in Mead. There are generic tannins that are mostly derived from grape skins and seeds, then there are other blends from various oaks, nut shells (chestnuts come to mind), as well as proprietary blends of grape skins and seed tannins.. There are some designed for adding during fermentation, some for bulk aging, and some that are for 'final tweaks' when closer to bottling time. With meads taking their sweet time to age, most dont try to drag it out any further by throwing tannins in the party (I'm not 'most' lol) as they take time to integrate and 'fall into line' so to say. Not uncommon for a mead to take 3-5 years to Shine (this doesnt mean 'drinkable'/can choke it down, this refers to the Mead saying, "Hey! pick me pick me! I'm ready!").. Add tannins, and add a few more years most likely.. Not something I'm personally scared of, but not something most attempt on their first batch or two.
There's a whole slew of yeasts to choose from, once you get comfortable with the basic. They all have different ABV Tolerances, meaning you've got to adjust your SG accordingly or run the risk of an ABV-bomb or something syrupy sweet because the yeast gave up waaay earlier than you anticipated. All these different yeasts also bring different aromas and flavors to the party - some are light, crisp and rather neutral while other can throw some spice at you, while yet others can take that fresh raspberry and morph it into a sort of baked-raspberry sort of flavor. Yeast also, are highly affected by the temp of the must their working in, and each has tolerances that are different. It's looking at these differences overall, thats help us make generalizations on what temp to ferment - 70F is the 'sweet spot' because its on the high-side for white wines and on the low side for high-extraction red wines.. Meads? I try to ferment as cold as I can without constant interference (like adding frozen water bottles or something) because I believe a constant temp is better than a perfect temp.
Malo-Lactic bacteria is not really needed in Mead, but I brought it up because you'll consider it just about every where else once you've been exposed to its characteristics. I brought it up, because its probably one of the most nit-picky things you could try to work with; each strain has specific ABV, SO2 & pH requirements... And some yeast strains for primary fermentation make more SO2 than others - so choose the wrong strain of yeast and the right MLB, and the combo wont let the MLB do its job. Or if theres too many blackberries and the pH is through the floor at some 2.9 or something - its not going to work either if the pH tolerance of the MLB is 3.2+ ... Or if you want to MLB an 18% ABV wine? I cant even think of one that could handle anything over 16%..
WVMJ touched on oak - theres dust, chips, cubes, spirals (and barrels, but we're not just gonna wing one of those right out our backside lol); each type of oak has different extraction times, and is used/removed at different times during the fermentation depending on the hoped-for outcome. Dust and chips usually end up in primary fermentation while the rest are generally added later. Each type of oak is also different in the aspect of where it came from, and the amount of 'toast' they gave it - these change the characteristics of the wood itself, which alters its impact in the wine/mead.
There's also the oddball additions you can make during anaerobic fermentation (under airlock) or during bulk aging - things like chocolate, vanilla beans, raisins or dried fruits..
There's also the Bochet method that a bunch of us have been trying lately.. It deals with bringing the honey to a boil for anywhere between 30-90 minutes, but this takes that light floral honey you're used to and changes it into a beast full of caramel, campfire, marshmellow, coffee and toffee type flavors.. An entirely different animal, yet a blast to make (careful, can be a quite-literal interpretation.. Boiling honey is dangerous without proper handling and can spit and sputter all over you and your kitchen if you're not careful... think of tiny napalm bombs flinging at ya lol)
I could write a book on any of the things I've brought up, and amongst all of this writing, I've probably forgot quite a few things.. But if anything jumps out at you either here or on some other page on the Web.. If you're at all, in any way, unsure of whats really going on - please ask. It's much easier to try to point you in the right direction before hand than it is to have a community effort to try and fix a fault ('cause thats what happens.. Hydrometers anyone?

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Let us know, and we'll do what we can to help you amaze yourself.