Question

Read the line from "Do not go gentle into that good night." Wild men who caught and sang the sun in flight, The meter, if any, from this line is

Answer 1

it is iambic pentameter

Answer 2

The meter from this line is pentameter, and to be more precise, this is an iambic pentameter.
Iambic means that the first syllable in the line is unstressed, and that it is followed by a stressed one. Here, you can see that DO in the beginning is unstressed, and the accent is placed on the second syllable, NOT. Pentameter means that there are five meters (penta means 5), and given that one meter consists of 2 syllables approximately, pentameter consists of 10 syllables in each line.