In the heat of battle there are many things that cease to matter; The color of the sky, the songs of the bards, the history of the world, the only thing that is winning, surviving. This is when a tree isn’t just a tree, its safety, a table is cover waiting to happen, the thick volcanic smoke is a 20% miss chance. When the fur starts flying and the dice start rolling what matters is the tactical advantage of every move, but that doesn’t mean battle isn’t a great place to inject some scenery, in fact it’s the best place.
In a regular tavern the players may not care whether their table is finished wood, whether it’s thick or thin, but if a fight starts suddenly those details are more important. Every difficult terrain, every partial, regular or total cover, every high ground and concealment is a chance to inject scenery and life into your world while making your players keenly aware of it. If they want something to tie up the thugs they just bludgeoned offer up the lord’s banner with the snake sigil on it, or the table cloth spun from pressed banner wood fibers. When the player wants to hide in the forest let them know they’re taking refuge in the deep black boughs of a mighty howler pine native only to the nation of Abysmia.
Those examples though require a great deal of thought put into the setting and detailed backgrounds and that is not everyone’s cup of tea. Even if the details of the local area are pretty vague feel free to add something suddenly, make up an interesting detail, or pull on what little you do know about the area, the important thing is that hiding behind “A rock” only tells that rocks are found here. But ducking behind “A shrine to the stone mother Alehjin” tells the player about the local gods, about the feeling of the area, and depending on the faith of the party can change the way they feel about taking shelter and how they react to their assailant toppling their cover.
Even if you must rely on very basic terrain features take effort to give them a one sentence description, something that makes them feel alive and exciting. When the boulder being used for cover takes damage describe how it sounds when stone cracks, when the players duck into the volcanic smoke describe the burning scent stinging their eyes, make it vivid but keep it short.
And when there are options to use terrain make sure the players understand that these objects are there to be used if desired, after a few times making effort to do this it will become natural and instinctive. Before long your players will recognize and remember that this region of the land has tall reeds great for hiding, or jagged rough terrain ideal for ambushes and cover. Being able to blend world building, immersion, and combat effectiveness and bonuses is always a win-win for DM’s and players alike.