Abstract: Axion Like Particles (ALP) can be a viable solution to the dark matter problem in a wide range of masses. Their interaction with photons provides a rich phenomenology and enables us to search for them with many different instruments across the electromagnetic spectrum. In this talk I will first review the birefringence effect produced by ALP DM and the search for this effect with radio and microwave telescopes. And second, their decay that could leave an imprint on em spectra and in particular the hunt for this line in the infrared band.