I have just participated in this market a few recent months and begin with some BTC. I am saving them in my cold wallet and I'm wondering how to bridge my BTC to another chains such as Ethereum, Polygon to get more profit from Defi. Please help me and give me some good ways (reasonable cost and safe) to do that. Thank all!
You need to use dapps bridge specific on the blockchain you are using because you will meed to lock your native Bitcoin to a smart contract to get an equivalent wrapped Bitcoin on your desired blockchain.
If your purpose is just trading then why not use the native token of the specific blockchain that you will use to save time for getting separate transaction fee. Then just buy WBTC on that specific blockchain DEX if you want to hold Bitcoin on that Blockchain. Bridging native Bitcoin to WBTC is a bit tricky and some bridge doesnt have this feature.