Like human form as a blue skinned deity . Having four arms , and very beautiful form. Does Lord vishnu really look like this , or is this metaphor ? metaphor as in 4 arms means omnipotence of Brahman in four directions and beautiful form means brahman is "beautiful" ? but brahman is formless.
Yes, Lord Vishnu looks exactly like how he is described. One who has progressed well in meditation gets Darshan of Gods. Swami Sivananda had shed some light on the experiences one gets.
Meditation / Experiences in Meditation / Jyotirmaya Darshan:
When you advance in meditation you can see your Ishta Devata in physical form. Lord Vishnu will give you Darshan with four hands; Lord Krishna will appear before you with flute in His hands; Rama with bow and arrow in his hands; Lord Siva with trident and Damaru.