How are metta and dana related? In accord to Dhamma, What is appropriate to give oneself? 

What is appropriate to give to others?  

Does dana ever go to oneself? Could 
 oneself be  seen  impersonally as another that needs  dana? How is    metta and dana related or not related?
'Dana' can be a 'test' of true 'metta'. For example, the Christian Bible refers to 'metta' without 'dana' as being something 'dead', as follows:

Suppose a brother or sister is without clothes and daily food. If one of you tells him, “Go in peace; stay warm and well fed,” but does not
provide for his physical needs, what good is that ? So too, faith by
itself, if it is not complemented by action, is dead.…
James 2:16

The Pali suttas often refer to 'dana' as follows:

... devoid of the stain of stinginess, freely generous, open-handed, delighting in relinquishment, devoted to charity, delighting in giving and sharing
SN 11.11

'Dana' can show we have true metta towards others rather than the fake metta of politicians, virtue signallers and social justice warriors.