Restaurant near Lyric Opera House
The Lyric is in the Mt Vernon neighborhood, near the border with Bolton Hill so anything in northern Mt Vernon is walkable.
I second AussieWonder's recs, including avoiding Sammy's.
Don't forget the options at Station North, which are also walkable to the Lyric: Zodiac (one of my faves) and Tapas Teatro. Zodiac you can sit and linger, Tapas you will have to wait for a table and it's generally always packed.
b in Bolton Hill is also an option.
Not sure what type of food you're after but last week I ate at Dionysus on Preston street, between Charles and St Paul and thoroughly enjoyed the Gourmet Bangers and Mash - three different types of sausage: pheasant, bison, venison - tasty.
On Charles Street there's the Brewers Art where you can choose from the bar menu or the full restaurant menu, both are good but the latter is pricier.
There's the Ethiopian "Dukem" on Maryland Ave, next to the parking garage for the Lyric/Meyerhoff. Personally, not a fan of this ethnic cuisine but they have a good reputation and are well respected.
I'd avoid Sammy's Trattoria on Charles, large portions of relatively bland Italian (IMO).
I am not sure if the Abacrombie opened back up yet, think it might have but they've been going thru much teething w/ chefs so def call before you go.
Robert Oliver's seafood is ok - never really took off, but the bar is a nice place for a pre-show drink.
Owl bar two blocks up on Chase between St. Paul and Charles in the Belvedere Hotel is ok, although the last time i was there my burger was over cooked to death. They do pour heavy on cocktails - always a bonus!