I don't have any cows to offer but I can get you whatever else you want
Friends of mine, will you give me gifts for my love, Hippodameia?
I have some gifts for you.
Sure, I have a few cows for you.
Kill Medusa using the view in the reflection of your sword
Here are the treasures we have for you.
Perseus is Danae's son. Polydectes likes his mother and wants to marry her but is afraid that Perseus will get in the way.
Please don't kill her.
You will regret this.
So he asks his friends including Perseus for gifts to impress the woman he loves he he pretends to be Hippodameia, knowing that Perseus will not have any cows and get him whatever else he desires, and so he asks for the head of a Gorgon, which is basically a suicide mission. "He would go off and kill Medusa and bring back her head as his gift." (Hamilton 143)
You disrespect me and my family by not providing hospitality, so you shall pay forever as stone!
He asks nymphs for god treasures and receives Hade's helmet of invisibility and advice from Athena to use the reflection in his sword to kill Medusa and not look at her. "Before he attacked Medusa he must first be properly equipped, and that what he needed was in the possession of the nymphs of the North." (Hamilton 144)
He then goes to the gorgons and kills Medusa using the reflection of his sword, her sister then get angry and chase after him but he uses the helmet of invisibility to escape them. "For she alone of the three could be killed; the other two were immortal." (Hamilton 146)
On his way home he stops by where Atlas lives and there Atlas refuses to let him stay the night and therefore Perseus kills him by showing him Medusa's head and turning him to stone. "Perseus saw her and on the instant loved her." (Hamilton 148)
Perseus returns triumphant, gives Athena the head in thanks and doesn't have to worry about Polydectes trying to get rid of him anymore.