So to a point I try to have miniatures on hand, or at least stand ins for mobs, for combat purposes because it adds something to the game and can just help lay things out for the players.

But sometimes I also will just describe the action, for example, one time the party found themselves in an ocean being circled and attacked by a baby megalodon, so with playing the JAWS theme in the background I described how they could see fins rising and falling, feeling the shark brush against them. At the end the party was blown away as i was able to actually make them anxious as they felt like it was really happening.

My real question atm is how important are miniatures vs just describing the fight? Right now one of my villains basically has a nightmare beast as a pet that the party is getting ready to go toe to toe with but I cannot find a mini for it or even one that looks similar.

Thoughts?

If I can't use minis, I use coins, or paper scraps, or chess pieces, or minis from other games, or thumbtacks, or... well, you get the idea.

I personally find drawing out the basic idea of where they're fighting and what's going on, and where things are positioned relative to each other INVALUABLE.  It's SO much easier, and faster, than describing the scene again every 5 seconds because people aren't clear on it, and it makes player's turns go SO much faster because they can (and should) effectively plan what they want to do and be ready to go the moment their turn starts, instead of taking 5 minutes from the start of their turn to actually declare their 6 seconds worth of actions.

YMMV, but in my experience the only combats not worth setting up are those unlikely to last past a round.

I recently purchased dry-erase tiles to use as placeholders for monsters. 

I definitely recommend using SOMETHING to use on a grid to help keep encounters organized and fair. It helps players visualize their attacks. 

I have personally spent the vast majority of my roleplaying career (roughly 22 years now), both as a player and as a DM, playing with theater of the mind, i.e. with no minis nor maps/dry-erase board or the like.

While I can certainly see the usefulness and convenience of visual aids such as the ones above, I do not find them necessary at all, provided the party is able of abstraction and has a sufficient level of imagination.

I've been playing DnD for nearly 16 years now and about ten of those were spent being a DM and I have never used minis. The concept is good but my players all enjoy visualizing the fights in their minds and I do as well.

I find that miniatures are pretty useful, especially when dealing with very tactical fights and many players. I like them a lot and have plenty myself, but some fights though I don't think need them at all. Like LeK touched on, theater of the mind can be better. For example, it can speed up play while the use of miniatures, at least for me, tends to slow down encounters. Describing a fight with just words and imagination can be a fulfilling for both DM and player. With great storytelling and descriptions from a DM, the players can visualize what is happening. Ultimately it's up to group preference and what style of game is being run.

I just want to point out that using miniatures in no way shape or form Prevents someone from also visualizing the combat in the theatre of their mind.  It helps people be on the same page in that visualization, and helps people keep track of things, but it's just that- an aid, nothing more, nothing less.  As they say, a picture is worth 1000 words, and having a picture As Well As great visual descriptions from the DM, and the joy of using their words and imagination, can help things flow smoothly while being just as fulfilling.  If you and your players enjoy it more without them, more power to you, I'm not one to tell anyone that it's wrong to prefer what someone prefers.  If you haven't tried them however, I'd encourage you to do so.  Trust me, having some representation that there is a chair, table, 3 guards, prisoner, and the players in a dungeon cell doesn't preclude the fantastic descriptions of the smell of mildew permeating the atmosphere, the rotting hay used as bedding, the rusted nature of the iron bars, or any of the intricacies of combat, etc etc etc.  It does help prevent the "how many guards were there?" questions every 2 rounds and keeps people on the same track regarding who is in the cell and who is outside it, etc.  It's a tool.  Nothing more, nothing less, and if you *can* use it, I've rarely found it better to not do so, again, just my experience.

Honestly, I tend to use Roll20 as the grid, even when I'm running a game in-person, so I can just upload pictures to act as the "miniatures." Honestly, I wouldn't even bother with that, but too many game rules rely on range, area of effect, or movement speed. I admire anyone that can keep all that in their head without some kind of mini or stand-in, but I'm not one of them.

The reason I use the Roll20 grid is because there isn't any clean-up, and I don't have to worry about finding a mini for some obscure monster.

They aren't a must, but they can be a useful tool, especially if the players are confused about the layout of the place you are at.

I find them very useful, especially since we usually play with 5 to 6 players. It helps keep everything organized and spells out locations on the map and so on. I never used miniatures in my AD&D days, and while they are not mandatory, I don't think I would ever play without them again. I have a box of "villains" that one of my players bought for me and it is great. Simple paper images with stands that are not overly fancy but much less than buying hundreds of miniatures.

Quote from GiantOctopodes >>

I just want to point out that using miniatures in no way shape or form Prevents someone from also visualizing the combat in the theatre of their mind.  It helps people be on the same page in that visualization, and helps people keep track of things, but it's just that- an aid, nothing more, nothing less.  As they say, a picture is worth 1000 words, and having a picture As Well As great visual descriptions from the DM, and the joy of using their words and imagination, can help things flow smoothly while being just as fulfilling.  If you and your players enjoy it more without them, more power to you, I'm not one to tell anyone that it's wrong to prefer what someone prefers.  If you haven't tried them however, I'd encourage you to do so.  Trust me, having some representation that there is a chair, table, 3 guards, prisoner, and the players in a dungeon cell doesn't preclude the fantastic descriptions of the smell of mildew permeating the atmosphere, the rotting hay used as bedding, the rusted nature of the iron bars, or any of the intricacies of combat, etc etc etc.  It does help prevent the "how many guards were there?" questions every 2 rounds and keeps people on the same track regarding who is in the cell and who is outside it, etc.  It's a tool.  Nothing more, nothing less, and if you *can* use it, I've rarely found it better to not do so, again, just my experience.