Your military might or military ranking and how it relates to your final score is actually a very confusing topic. First off there are three different places where your military might or ranking is listed and it's actually listed in two different ways.
The following screenshot is from my most recent game where my final score was 924,500. Note that this was a DL game but all of this applies to DA and ToA as well.
In this screenshot of the Stats & Graphs area under your Civilization Manager, you can see the same information in two different ways. From your statement that your military might was 264 it seems that you're looking at the information from the military bar chart. You see this by selecting under the Military bar graph and then looking at the summary information highlighted in yellow.
This information is *not* your absolute military rating and can be very misleading. This is actually only your *relative* military rating when compared to the currently selected AI opponent, in my case the Terrans. This information can be important in and of itself. For example there are certain ways that an AI will act towards you dependent on this ratio being higher than 3 to 1 and then again at 10 to 1. But as far as your score this has nothing to do with anything.
Your *real* military rating is displayed by selecting the Military button under Abilities that's highlighted in light blue in the above screenshot. There are a number of things displayed here that are of interest. The first thing is your total number of ships. In my case it lists 19,471 ships. What's most interesting about this figure is that it's wrong. By looking at my Ship Yard display I really have only 17,037 total ships. This is not particularly important it's just yet another source of confusion.
The other pieces of information that are useful are how much you're spending on Ship Maintenance (in my case 3.6 million bc per turn), and the most important piece of information in terms of your final score is the Military Ranking (in my case 14.1 million).
I previously mentioned that there are three places your military ranking is displayed and the final place is really the most important when it comes to score. This is shown in the following screenshot that shows the graph of your military ranking over the course of the entire game. This is displayed under the Timeline tab of your Civilization Manager.
Basically your military score is determined by this graph. The short description is that your military score is based on the "front end weighted", "area under the curve". By "front end weighted" I mean that you get more credit in your final score for early values of military rating versus later values of military rating. By "area under the curve" I mean that your final score is dependent on having high values of military rating that need to be held for long periods of time. For example you could possibly achieve a very large military rating right before you end the game and you would hardly notice the effect it will have to your score.
Note that these same things apply to the other three components of score; population, income and research spending, but that's a different topic.
Looking at the military graph is very instructive. Basically everything related to score can be read directly from this graph if you know what you're doing.
Basically my military strategy involves building many thousands of 1 attack 1 defense huge hull ships to place under an array of 24 military starbases each of which give a 63 point bonus to each of my ships. The total bonus given to each ship by such an array is 24*63=1512. In my case I "build" about 300 such ships per turn for a period of about a year and by the end of that year I have about 17K such ships.
The stairstep action that you see early in the curve is due to how I go about moving my ships from the planet that built them to under my military SB array. To avoid having many hundreds of individual ships moving one at a time to my military SB array, I wait 7 or 8 turns leaving the ships sitting by the planet that built them. Once I have a fleet worth of ships then I fleet them up and send them off to under my array. That’s where you see the big jump in military rating.
But if you look closely you’ll see that while I’m building more ships that sit next to the planet that built them my military rating doesn’t just stay the same or increase by a little bit, my military rating actually *goes down* during this period. This brings up another very important point. Your military rating is determined in part by some function of how strong your ships are based on attack value, defense value and hit points. But besides that it’s divided by some function of the total number of ships that you have.
The reason that my military rating declines slightly is because while the ships are sitting by the planet that built them they are of a very low value. The low value doesn’t contribute much to the sum of attack plus defense plus hit points but it does increase the total number of ships and so the military rating declines. Once all ships are moved to under my military SB array then the military rating shoots back up.
Because of this, for maximum score, you want the highest possible military rating with the fewest possible number of ships. To achieve that once I get around 17 thousand 1 attack / 1 defense ships I then do a massive upgrade to the most powerful ship that I can build. Note that this is dependent on what kind of attack and defense bonus that I have which is itself dependent on the number of military resources that I have to mine. In most cases people usually have slightly higher defense bonuses than weapons bonus and so the upgrade ship that I use consists of 1 Black Hole Eruptor and then as many Zero Point Armors as I can fit on the huge hull. Note that this is why I initially build my 1/1 fighter based on a huge hull so that I can get maximum points out of my final upgrade.
From the graph you see the tremendous boost that I get in my military rating in one turn from this upgrade. In the case of this game my military rating was about 5.7 million prior to the upgrade and 14.1 million after the upgrade.
One final point is that the vertical axis displays your maximum military rating but only the first four significant digits are shown. However you can see the 1410 listed in this graph which correlates to the military rating of 14.1 million from the Stats & and Graphs page.
This is everything you could possibly ever need to know about Military Might and Metaverse Score.