Not voluntarily you can't, only when instructed to by a card effect.
One of them for sure is Lightning Vortex.
You can't ever just discard cards for no reason, you can only do so if instructed to by a card effect or a game rule, such as the one that lets you replace one Field Spell Card with another.
If you have a treasure card(s) in your deck, you will need to discard one card in your deck to draw a treasure card. Right click on a card to discard, then if you have a treasure card(s) in your deck, the "Draw" button at the bottom will be clickable, and this will draw one random treasure card into your hand when you click on them. You will need to discard one card to draw one treasure card, so if you need two treasure cards, discard two cards in your hand and click the Draw button two times.
download a new one
Discard and replace it - do not attempt to fix it
There is no limit to the number of cards in your hand at any one time, however, you must discard down to 6 at the end of the End Phase of your own turn. At any other time, it doesn't matter. So if you have five cards in hand, and your opponent bounces two or more into your hand, that's ok. So you have 7 now. Your turn draw will make it 8, but it won't matter unless you still have 7 or more when you reach the end of your end phase, which will make you have to discard.
Discard it and get yourself a new one.
The word 'discard' is both a noun (discard, discards) and a verb (discard, discards, discarding, discarded).The noun 'discard' is a word for someone or something rejected as no longer useful or desirable; a word for a person or a thing.The verb 'discard' is to get rid of as useless or unwanted; to remove a playing card from one's hand; a word for an action.
In Canasta, to go out, you must have at least one meld of 50 points or more and have played all your cards. You can discard any card from your hand, but you must ensure that the discard does not break any melds you have created. Additionally, you can only go out if you have met the game's requirements for melds and have no cards remaining in your hand after your final play.
Dark paladin's effect is you can discard one card from your hand to stop a spell card from being activated
The answer is NO. If there is a cost requiring you to discard a card, you cannot play it. You also can't, for example, play a Card Destruction if there are no cards in either players hand or play Raigeki when your opponent controls no monsters.
The one from the tin? A few £, maybe.