If the spectrum of a star shows the same absorption lines as the sun what can be said about the stars composition?

When stars form in the present Milky Way galaxy they are composed of about 71% hydrogen and 27% helium,[87] as measured by mass, with a small fraction of heavier elements. Typically the portion of heavy elements is measured in terms of the iron content of the stellar atmosphere, as iron is a common element and its absorption lines are relatively easy to measure. Because the molecular clouds where stars form are steadily enriched by heavier elements from supernovae explosions, a measurement of the chemical composition of a star can be used to infer its age.[88] The portion of heavier elements may also be an indicator of the likelihood that the star has a planetary system.[89]

The star with the lowest iron content ever measured is the dwarf HE1327-2326, with only 1/200,000th the iron content of the Sun.[90] By contrast, the super-metal-rich star μ Leonis has nearly double the abundance of iron as the Sun, while the planet-bearing star 14 Herculis has nearly triple the iron.[91] There also exist chemically peculiar stars that show unusual abundances of certain elements in their spectrum; especially chromium and rare earth elements

Edit : That's interesting, but it doesn't answer the question. The answer is that

the star and the Sun must have the same chemical elements in their "atmospheres".