Steel HO: a concept
A background on the idea
Through experience with nat dex mono, or any mono tier in general, you become accustomed to the general archetypes a type can run, or what is usually most optimal. For example, poison at its best is semi stall usually, bug, hyper offense, and so forth. Steel is no exception to this. After all, it's usually a balance team that abuses what I think is one of the most comically stupid combinations in the game, that being, the dreaded immunity core.
So now that you've already read the title, you're thinking, "what's the deal with steel HO? Why would I run such an awkward archetype for this given type? I'm stripping myself of the ability to use the defensive profile of the team to the fullest, and so forth? Why bother go to this effort?" I'm probably just gonna have more success with a sample steel balance team or something like that right?
And the simple answer is: It's fun. It's a concept that turns the idea of how steel is perceived, on its head to make something that is unorthodox, yet, in its ways, effective.
So with that being said, allow me to present the team, the building process, matchups, and other considerations.
Note: this isn't necessarily a brand new idea. Steel HO has existed for a bit of time, although rarely, as it is overshadowed by the superior steel immunity core balance structure. I'm simply just focusing the spotlight on this fun idea.
So here's the team that I've rolled with for a while:
https://pokepast.es/55c0162f43dea1cd
Teambuilding
Where do we start? Well, like most HO teams, you gotta have a suicide lead. And a few options came to mind.

Skarmory has been known as a potential lead for a few generations. Access to both rocks and spikes, taunt, brave bird recoil to take itself out if at low, it's a classic example of a suicide lead. This lead in fact dates back to the gen 5 OU days. Klefki is a bit uncommon and only has spikes as the hazard of choice, but brings something else to the table: dual screens. Knowing how heavily focused HO teams are on set up, screens can prove to be quite potent, especially since steel has solid offensive set up options. Excadrill is a bit more common when considering the OU tiers. Rapid spin to deny opponents hazards, rocks of your own, and other unique tools such as rock tomb, steel beam, etc. My choice here was skarmory, since I thought it was cooler and I did like the throwback to gen 5 OU. Excadrill here also has a different purpose on my team (you'll see later).
Next I needed some physical attackers to choose from.

All of these options are generally very solid since they all have something unique to bring to the table. Mega scizor has the priority in bullet punch which is always appreciated, and has a nice coverage movepool for certain targets of your choice, from bug bite, superpower, knock off to dual wingbeat. Bisharp has a very nice dark stab in knock off and priority, both which are generally spammable and also has the defiant ability, which is great to deter defog attempts from the opponent, especially since you want to stack hazards with the HO lead at the beginning. Lucario has fighting stab, which may be important to break opposing bulky steel teams which might wall a steel HO team like this, while also packing priority, boosting moves and great coverage on both sides of the spectrum (special or physical). Aegislash also packs priority and swords dance like the others, which seems to be the trend now, but unlike the others, packs some important defensive utility in being a part ghost type, allowing it to be the team's fighting immunity and rapid spin blocker, another way to block hazards. Here I decided to use mega scizor cause I wanted a mega on the team and I elected to use bisharp since I liked how potent it could be at preventing hazard removal, since defog is usually a bit more expected in the meta compared to rapid spin.
Now for the special attackers:

Jirachi here has important psychic typing for a fighting neutrality, and stab psychic moves to of course threaten those fighting types. A calm mind set is feasible, but since we're in nat dex mono, it would be even more fun to use a z happy hour set with this pokemon. Celesteela has been known for two things, either a defensive leech protect set, or an offensive autotomize sweeper, and knowing the theme, it shouldn't be hard to figure out what set we're choosing here. The ground immunity is also appreciated. Lucario doesn't really need too much introduction since it was talked about earlier. Priority, nasty plot, fighting stab, you get the idea. I chose the first two cause the utility they have in certain matchups can prove to be quite useful, and also I believe they would end up being much more fun to use. Z happy hour jirachi is a comically effective pokemon between its decent power and flinch happy iron head. Celesteela got a new toy in meteor beam which does a lot of damage, especially when you consider that you usually hit with a plus 1 meteor beam when it activates due to how the move works.
The last option:
Last but not least, excadrill

I had a specific set for this pokemon since I had a specific use for it on the team. Firstly, the defensive or offensive utility it provided was useful. Electric immunity and ground stab meaning it would not only block volt switch (which would otherwise be spammed against the team), but also a way to deal big damage to electric teams. It also hits most steels which is good in order to break most of them. It's ground stab alongside rock slide also creates perfect coverage to hit fire types. But you might be thinking, how would it get the opportunity against fire teams. So many of the options they have are quite fast. Well, that's where the hidden trick comes in: focus sash. With swords dance, a buffed rapid spin, it can the opportunity to get a set up on fire and potentially beat them. It's not perfect, but it's something (fire is usually dead for this team anyways, as per most if not every steel team that exists).
Matchups
This post is already long as is so I'm just gonna quickly go over some matchups that are interesting or just straight up bad for the team and what could be done.
Fire: this should be a no brainer. It's even worse now that there's no heatran on this current version. Best bet is to anti-lead the torkoal they usually carry with exca, and attempt to dent them with your moves.
Water: ever wondered why steel packs ferro? Yeah, this is why. A team that has no water resists, versus a team that likes to abuse rain boosted stab attacks from mega swampert, urshifu, manaphy and the likes, is a very bad recipe for this team. It's even worse cause they're likely to outspeed you. Somehow, you wanna get hazards up to force chip, and if you ever predict a defog coming in, switch in bisharp immediately. Also aim to get rid of urshifu as fast as possible as it is the mon likely to shred the team first.
Fighting: steel vs fighting, yeah, should be bad. Can be possible if you get jirachi and celesteela set up. Scizor might also do some work here. Those are the main wincons
Ghost: This is where you don't lead skarm since mega sableye is likely going to block any hazard attempt. Rapid spinning with exca also is not possible here. You probably just want to attempt to break sableye with celesteela and don't let bisharp get burned.
Dragon: a bit like fighting mainly cause kommo-o is actually the scariest thing about the team vs you. A fun fact, plus 1 flamethrower does not OHKO jirachi, meaning after a sac, you boost up with jirachi and kill it back the next turn
Bug: this isn't as easy as it is on face value. You no longer have a switch into volcarona and scarfed buzzwole/hera will likely cleave through. Celesteela is of course important here since it has the coverage to destroy the team if you set it up correctly. Also preserve exca's sash for volc or preserve skarm if you haven't gotten rid of their spinner yet.
There are many other matchups vs this steel HO team, each with their own dynamic, but I'll leave it here for now since these are in my experience, the most interesting ones.
Other considerations
Steel HO as a concept is still relatively unexplored, and the team I have definitely is flawed in certain ways. I don't even think it's that optimised and that there could be some modifications to adapt for certain other matchups.

is still a great consideration since it completes the "hazard-proof core" alongside skarm with taunt, and bisharp. It also has the components you want for a physical sweeper with its priority and good coverage.

a special attacker, but not a set up sweeper, which is why I didn't introduce it earlier. Why do I bring it here? Cause it can run an offensive set for the team, whilst still contributing to the team defensively, courtesy of flash fire, which is the main selling point of heatran for this team. An air balloon set with magma storm, earth power, hidden power ice, and taunt can be effective for example.

I wanna stress something here, I am not underrating the power of screens. I've used them myself on other teams and know how effective they are. You don't even have to sacrifice your screens setter after getting them up, allowing you to get them up later in the game and make the set up of another mon easier. A more niche, but potentially deadly set is a calm mind iron defense magnet rise draining kiss set. Designed to lure and potentially 6-0 dragon or dark.
In general you could even fit other speed control, like a scarfer somewhere. There's just a lot you can do as long as you can fit it to what matchup you wanna have an edge against. Steel is versatile enough in its offensive options that you can tailor something to what you want. So by all means, explore the possibilities.
Conclusion
This post has been longer than I thought, and for a team that isn't exactly what you call tournament winning, or a high ladder team. If you wanted to win with a steel team at the top level, the steel balance structure is right there. But I've had a lot of fun with this team and I wanted to share it. I've thought about making this post for a while and I wanted to showcase this underrated idea. So take the team, customize it to your liking, and just have fun.
This has been my rendition of steel HO: a concept.
Next team I'll post here will probably be a lot shorter since it's something people are more familiar with.