What are some literary devices found in Lord Capulet's lines of Act IV, Scene 5 of Romeo and Juliet? What significance do these devices have?

The short answer is that nearly every word that Capulet utters here is filled with literary devices that propel the tension and mood, build the dramatic irony, and develop the audience's sense of who Capulet is. Let's look at the details.

In Act 4, Scene 5, the Nurse and Juliet's mom, Lady Capulet, find Juliet's body and believe her to be dead.

When Juliet's dad, Capulet, walks in and doesn't know what's going on yet, he says:

"For shame, bring Juliet forth. Her lord is come."

What he means is, "Get Juliet. Her soon-to-be husband is here." But because the word "lord" can mean different things, it kind of sounds like he's saying that God has come to get her. It's kind of a dark and funny play on words. When words can mean two or more different things and they're used ambiguously in this way, it's a literary device called double entendre. In this case, its significance is creating a darkly humorous scene.

When he realizes what's going on, Capulet is understandably distraught, and he says:

"Death lies on her like an untimely frost

Upon the sweetest flower of all the field."

Here, Capulet uses a simile (comparing death to a frost) and a metaphor (comparing his daughter to a flower--which he's actually done before, implying that she's precious, beautiful, delicate, innocent, and so on). The effect of these figurative comparisons is that they establish a mood of dramatic grief, they build up the dramatic irony because the audience knows Juliet isn't really dead, and they further develop Capulet's character by showing his soft side.

Here's the next thing he says:

"Death, that hath ta'en her hence to make me wail,

Ties up my tongue and will not let me speak."

Here Capulet means, "Death, you've taken her away from me to make me cry, but now you've tied up my tongue so I can't speak."

A couple of devices are in play right here. First, when you dramatically address someone or something that isn't actually there, like Death, it's called apostrophe. It's a literary device that can express heights of sadness and frustration, which is what's going on here.

Second, look at how Capulet is saying "I'm so upset that I can't even talk," and yet he's talking a lot! On the surface, this is understandable. He thinks his daughter is dead, so he's not talking sense. But also, it's pretty funny. When there's a striking or funny contrast between what's being said and what's actually true, you can call it verbal irony. Here, its effect seems to simply be humor.

After that, Capulet says this to Paris, the guy who's supposed to be marrying Juliet that day:

"The night before thy wedding day

Hath death lain with thy wife. There she lies,

Flower as she was, deflowered by him."

Yikes! He means "Right before you were supposed to get married, Death slept with your intended wife. And there she is. She was a flower, but Death deflowered her."

He's saying that death has "deflowered" Juliet, or taken her virginity. It's another play on words (specifically another double entendre) that builds the tension at the same time that it adds humor.

After that, he does a lot of (understandable) wailing and moaning, followed by some intense repetition in the syntax which keeps on expressing the extent of his grief:

"Our instruments to melancholy bells,

Our wedding cheer to a sad burial feast.

Our solemn hymns to sullen dirges change,

Our bridal flowers serve for a buried corse."